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The Ethereal FAQ
Note: This is just an ASCII snapshot of the faq and may not be up to
date. Please go to http://www.ethereal.com/faq.html for the up
to date version. The version of this snapshot can be found at
the end of this document.
INDEX
General Questions:
1.1 Where can I get help?
1.2 How much does Ethereal cost?
1.3 Can I use Ethereal commercially?
1.4 Can I use Ethereal as part of my commercial product?
1.5 What protocols are currently supported?
1.6 Are there any plans to support {your favorite protocol}?
1.7 Can Ethereal read capture files from {your favorite network
analyzer}?
1.8 What devices can Ethereal use to capture packets?
1.9 How do you pronounce Ethereal? Where did the name come from?
Downloading Ethereal:
2.1 I downloaded the Win32 installer, but when I try to run it, I get
an error.
2.2 When I try to download the WinPcap driver and library, I can't get
to the WinPcap Web site.
Installing Ethereal:
3.1 I installed an Ethereal RPM, but Ethereal doesn't seem to be
installed; only Tethereal is installed.
Building Ethereal:
4.1 The configure script can't find pcap.h or bpf.h, but I have
libpcap installed.
4.2 Why do I get the error
dftest_DEPENDENCIES was already defined in condition TRUE, which
implies condition HAVE_PLUGINS_TRUE
when I try to build Ethereal from SVN or a SVN snapshot?
4.3 The link fails with a number of "Output line too long." messages
followed by linker errors.
4.4 The link fails on Solaris because plugin_list is undefined.
4.5 The build fails on Windows because of conflicts between winsock.h
and winsock2.h.
Using Ethereal:
5.1 When I use Ethereal to capture packets, I see only packets to and
from my machine, or I'm not seeing all the traffic I'm expecting to
see from or to the machine I'm trying to monitor.
5.2 I can't see any TCP packets other than packets to and from my
machine, even though another analyzer on the network sees those
packets.
5.3 I'm only seeing ARP packets when I try to capture traffic.
5.4 I'm running Ethereal on Windows; why does some network interface
on my machine not show up in the list of interfaces in the
"Interface:" field in the dialog box popped up by "Capture->Start",
and/or why does Ethereal give me an error if I try to capture on that
interface?
5.5 I'm running Ethereal on Windows; why do no network interfaces show
up in the list of interfaces in the "Interface:" field in the dialog
box popped up by "Capture->Start"?
5.6 I'm running Ethereal on Windows; why doesn't my serial port/ADSL
modem/ISDN modem/show up in the list of interfaces in the "Interface:"
field in the dialog box popped up by "Capture->Start"?
5.7 I'm running Ethereal on a UNIX-flavored OS; why does some network
interface on my machine not show up in the list of interfaces in the
"Interface:" field in the dialog box popped up by "Capture->Start",
and/or why does Ethereal give me an error if I try to capture on that
interface?
5.8 I'm running Ethereal on a UNIX-flavored OS; why do no network
interfaces show up in the list of interfaces in the "Interface:" field
in the dialog box popped up by "Capture->Start"?
5.9 Can Ethereal capture on (my T1/E1 line, SS7 links, etc.)?
5.10 How do I put an interface into promiscuous mode?
5.11 I can set a display filter just fine, but capture filters don't
work.
5.12 I'm entering valid capture filters, but I still get "parse error"
errors.
5.13 I saved a filter and tried to use its name to filter the display,
but I got an "Unexpected end of filter string" error.
5.14 Why am I seeing lots of packets with incorrect TCP checksums?
5.15 I've just installed Ethereal, and the traffic on my local LAN is
boring.
5.16 When I run Ethereal on Solaris 8, it dies with a Bus Error when I
start it.
5.17 When I run Ethereal, I get an error
Gtk-CRITICAL **: file gtkwindow.c: line 3107 (gtk_window_resize):
assertion `height > 0' failed.
5.18 When I run Tethereal with the "-x" option, it crashes with an
error
"** ERROR **: file print.c: line 691 (print_line): should not be
reached.
5.19 When I run Ethereal on Windows NT, it dies with a Dr. Watson
error, reporting an "Integer division by zero" exception, when I start
it.
5.20 When I try to run Ethereal, it complains about
sprint_realloc_objid being undefined.
5.21 I'm running Ethereal on Linux; why do my time stamps have only
100ms resolution, rather than 1us resolution?
5.22 I'm capturing packets on {Windows 95, Windows 98, Windows Me};
why are the time stamps on packets wrong?
5.23 When I try to run Ethereal on Windows, it fails to run because it
can't find packet.dll.
5.24 I'm running Ethereal on Windows NT/2000/XP/Server; my machine has
a PPP (dial-up POTS, ISDN, etc.) interface, and it shows up in the
"Interface" item in the "Capture Options" dialog box. Why can no
packets be sent on or received from that network while I'm trying to
capture traffic on that interface?
5.25 I'm running Ethereal on Windows 95/98/Me, on a machine with more
than one network adapter of the same type; Ethereal shows all of those
adapters with the same name, but I can't use any of those adapters
other than the first one.
5.26 I'm running Ethereal on Windows, and I'm not seeing any traffic
being sent by the machine running Ethereal.
5.27 I'm trying to capture traffic but I'm not seeing any.
5.28 I have an XXX network card on my machine; if I try to capture on
it, my machine crashes or resets itself.
5.29 My machine crashes or resets itself when I select "Start" from
the "Capture" menu or select "Preferences" from the "Edit" menu.
5.30 Does Ethereal work on Windows Me?
5.31 Does Ethereal work on Windows XP?
5.32 Why doesn't Ethereal correctly identify RTP packets? It shows
them only as UDP.
5.33 Why doesn't Ethereal show Yahoo Messenger packets in captures
that contain Yahoo Messenger traffic?
5.34 Why do I get the error
Gdk-ERROR **: Palettized display (256-colour) mode not supported on
Windows.
aborting....
when I try to run Ethereal on Windows?
5.35 When I capture on Windows in promiscuous mode, I can see packets
other than those sent to or from my machine; however, those packets
show up with a "Short Frame" indication, unlike packets to or from my
machine. What should I do to arrange that I see those packets in their
entirety?
5.36 I'm capturing packets on a machine on a VLAN; why don't the
packets I'm capturing have VLAN tags?
5.37 How can I capture raw 802.11 packets, including non-data
(management, beacon) packets?
5.38 How do I capture on an 802.11 device in monitor mode on Linux?
5.39 How do I capture on an 802.11 device in monitor mode on FreeBSD?
5.40 How do I capture on an 802.11 device in monitor mode on NetBSD?
5.41 I'm trying to capture 802.11 traffic on Windows; why am I not
seeing any packets?
5.42 I'm trying to capture 802.11 traffic on Windows; why am I seeing
packets received by the machine on which I'm capturing traffic, but
not packets sent by that machine?
5.43 How can I capture packets with CRC errors?
5.44 How can I capture entire frames, including the FCS?
5.45 Why does Ethereal hang after I stop a capture?
5.46 How can I search for, or filter, packets that have a particular
string anywhere in them?
5.47 How do I filter a capture to see traffic for virus XXX?
General Questions
Q 1.1: Where can I get help?
A: Support is available on the ethereal-users mailing list.
Subscription information and archives for all of Ethereal's mailing
lists can be found at http://www.ethereal.com/lists
Q 1.2: How much does Ethereal cost?
A: Ethereal is "free software"; you can download it without paying any
license fee. The version of Ethereal you download isn't a "demo"
version, with limitations not present in a "full" version; it is the
full version.
The license under which Ethereal is issued is the GNU General Public
License. See the GNU GPL FAQ for some more information.
Q 1.3: Can I use Ethereal commercially?
A: Yes, if, for example, you mean "I work for a commercial
organization; can I use Ethereal to capture and analyze network
traffic in our company's networks or in our customer's networks?"
If you mean "Can I use Ethereal as part of my commercial product?",
see the next entry in the FAQ.
Q 1.4: Can I use Ethereal as part of my commercial product?
A: As noted, Ethereal is licended under the GNU General Public
License. The GPL imposes conditions on your use of GPL'ed code in your
own products; you cannot, for example, make a "derived work" from
Ethereal, by making modifications to it, and then sell the resulting
derived work and not allow recipients to give away the resulting work.
You must also make the changes you've made to the Ethereal source
available to all recipients of your modified version; those changes
must also be licensed under the terms of the GPL. See the GPL FAQ for
more details; in particular, note the answer to the question about
modifying a GPLed program and selling it commercially, and the
question about linking GPLed code with other code to make a
proprietary program.
You can combine a GPLed program such as Ethereal and a commercial
program as long as they communicate "at arm's length", as per this
item in the GPL FAQ.
Q 1.5: What protocols are currently supported?
A: There are currently 602 supported protocols and media, listed
below. Descriptions can be found in the ethereal(1) man page.
3GPP2 A11
802.1q Virtual LAN
802.1x Authentication
AAL type 2 signalling protocol - Capability set 1 (Q.2630.1)
ACN
AFS (4.0) Replication Server call declarations
AIM Administrative
AIM Advertisements
AIM Buddylist Service
AIM Chat Navigation
AIM Chat Service
AIM Directory Search
AIM E-mail
AIM Generic Service
AIM ICQ
AIM Invitation Service
AIM Location
AIM Messaging
AIM OFT
AIM Popup
AIM Privacy Management Service
AIM Server Side Info
AIM Server Side Themes
AIM Signon
AIM Statistics
AIM Translate
AIM User Lookup
ANSI A-I/F BSMAP
ANSI A-I/F DTAP
ANSI IS-637-A (SMS) Teleservice Layer
ANSI IS-637-A (SMS) Transport Layer
ANSI IS-683-A (OTA (Mobile))
ANSI IS-801 (Location Services (PLD))
ANSI Mobile Application Part
AOL Instant Messenger
ARCNET
ASN.1 decoding
ATM
ATM AAL1
ATM AAL3/4
ATM LAN Emulation
ATM OAM AAL
AVS WLAN Capture header
AX/4000 Test Block
Ad hoc On-demand Distance Vector Routing Protocol
Address Resolution Protocol
Aggregate Server Access Protocol
Alert Standard Forum
Alteon - Transparent Proxy Cache Protocol
Andrew File System (AFS)
Apache JServ Protocol v1.3
Apple IP-over-IEEE 1394
AppleTalk Filing Protocol
AppleTalk Session Protocol
AppleTalk Transaction Protocol packet
Appletalk Address Resolution Protocol
Application Configuration Access Protocol
Art-Net
Async data over ISDN (V.120)
Authentication Header
BACnet Virtual Link Control
BEA Tuxedo
BSS GPRS Protocol
BSSAP/BSAP
Banyan Vines ARP
Banyan Vines Echo
Banyan Vines Fragmentation Protocol
Banyan Vines ICP
Banyan Vines IP
Banyan Vines IPC
Banyan Vines LLC
Banyan Vines RTP
Banyan Vines SPP
Basic Encoding Rules (ASN.1 X.690)
Bearer Independent Call Control
Bi-directional Fault Detection Control Message
Blocks Extensible Exchange Protocol
Blubster/Piolet MANOLITO Protocol
Boardwalk
Boot Parameters
Bootstrap Protocol
Border Gateway Protocol
Building Automation and Control Network APDU
Building Automation and Control Network NPDU
CCSDS
CDS Clerk Server Calls
Cast Client Control Protocol
Check Point High Availability Protocol
Checkpoint FW-1
Cisco Auto-RP
Cisco Discovery Protocol
Cisco Group Management Protocol
Cisco HDLC
Cisco Hot Standby Router Protocol
Cisco ISL
Cisco Interior Gateway Routing Protocol
Cisco NetFlow
Cisco SLARP
Cisco Session Management
Clearcase NFS
CoSine IPNOS L2 debug output
Common Industrial Protocol
Common Open Policy Service
Common Unix Printing System (CUPS) Browsing Protocol
Compuserve GIF
Configuration Test Protocol (loopback)
Connectionless Lightweight Directory Access Protocol
Coseventcomm Dissector Using GIOP API
Cosnaming Dissector Using GIOP API
Cross Point Frame Injector
Cryptographic Message Syntax
DCE Distributed Time Service Local Server
DCE Distributed Time Service Provider
DCE Name Service
DCE RPC
DCE Security ID Mapper
DCE/RPC BOS Server
DCE/RPC BUDB
DCE/RPC BUTC
DCE/RPC CDS Solicitation
DCE/RPC Conversation Manager
DCE/RPC Directory Acl Interface
DCE/RPC Endpoint Mapper
DCE/RPC Endpoint Mapper4
DCE/RPC FLDB
DCE/RPC FLDB UBIK TRANSFER
DCE/RPC FLDB UBIKVOTE
DCE/RPC ICL RPC
DCE/RPC Kerberos V
DCE/RPC NCS 1.5.1 Local Location Broker
DCE/RPC Operations between registry server replicas
DCE/RPC Prop Attr
DCE/RPC RS_ACCT
DCE/RPC RS_BIND
DCE/RPC RS_MISC
DCE/RPC RS_PROP_ACCT
DCE/RPC RS_UNIX
DCE/RPC Registry Password Management
DCE/RPC Registry Server Attributes Schema
DCE/RPC Registry server propagation interface - ACLs.
DCE/RPC Registry server propagation interface - PGO items
DCE/RPC Registry server propagation interface - properties and poli
cies
DCE/RPC Remote Management
DCE/RPC Repserver Calls
DCE/RPC TokenServer Calls
DCE/RPC UpServer
DCOM OXID Resolver
DCOM Remote Activation
DEC Spanning Tree Protocol
DFS Calls
DG Gryphon Protocol
DHCP Failover
DHCPv6
DICOM
DNS Control Program Server
DOCSIS 1.1
DOCSIS Appendix C TLV's
DOCSIS Baseline Privacy Key Management Attributes
DOCSIS Baseline Privacy Key Management Request
DOCSIS Baseline Privacy Key Management Response
DOCSIS Dynamic Service Addition Acknowledge
DOCSIS Dynamic Service Addition Request
DOCSIS Dynamic Service Addition Response
DOCSIS Dynamic Service Change Acknowledgement
DOCSIS Dynamic Service Change Request
DOCSIS Dynamic Service Change Response
DOCSIS Dynamic Service Delete Request
DOCSIS Dynamic Service Delete Response
DOCSIS Initial Ranging Message
DOCSIS Mac Management
DOCSIS Range Request Message
DOCSIS Ranging Response
DOCSIS Registration Acknowledge
DOCSIS Registration Requests
DOCSIS Registration Responses
DOCSIS Upstream Bandwidth Allocation
DOCSIS Upstream Channel Change Request
DOCSIS Upstream Channel Change Response
DOCSIS Upstream Channel Descriptor
DOCSIS Upstream Channel Descriptor Type 29
DOCSIS Vendor Specific Endodings
Data
Data Link SWitching
Data Stream Interface
Datagram Delivery Protocol
Decompressed SigComp message as raw text
Diameter Protocol
Digital Audio Access Protocol
Distance Vector Multicast Routing Protocol
Distcc Distributed Compiler
Distributed Checksum Clearinghouse Protocol
Distributed Network Protocol 3.0
Domain Name Service
Dynamic DNS Tools Protocol
ENTTEC
Echo
Encapsulating Security Payload
Endpoint Name Resolution Protocol
Enhanced Interior Gateway Routing Protocol
EtherNet/IP (Industrial Protocol)
Etheric
Ethernet
Ethernet over IP
Extensible Authentication Protocol
FC Extended Link Svc
FC Fabric Configuration Server
FCIP
FTP Data
FTServer Operations
Fiber Distributed Data Interface
Fibre Channel
Fibre Channel Common Transport
Fibre Channel Fabric Zone Server
Fibre Channel Name Server
Fibre Channel Protocol for SCSI
Fibre Channel SW_ILS
Fibre Channel Security Protocol
Fibre Channel Single Byte Command
File Transfer Protocol (FTP)
Financial Information eXchange Protocol
Frame
Frame Relay
GARP Multicast Registration Protocol
GARP VLAN Registration Protocol
GPRS Network service
GPRS Tunneling Protocol
GSM A-I/F BSSMAP
GSM A-I/F DTAP
GSM A-I/F RP
GSM Mobile Application Part
GSM SMS TPDU (GSM 03.40)
GSM Short Message Service User Data
General Inter-ORB Protocol
Generic Routing Encapsulation
Generic Security Service Application Program Interface
Gnutella Protocol
H.248 MEGACO
H225
H235-SECURITY-MESSAGES
H245
H4501
HP Extended Local-Link Control
HP Remote Maintenance Protocol
Hummingbird NFS Daemon
HyperSCSI
Hypertext Transfer Protocol
ICQ Protocol
IEEE 802.11 Radiotap Capture header
IEEE 802.11 wireless LAN
IEEE 802.11 wireless LAN management frame
ILMI
IP Device Control (SS7 over IP)
IP Over FC
IP Payload Compression
IP Virtual Services Sync Daemon
IPX Message
IPX Routing Information Protocol
IPX WAN
IRemUnknown IRemUnknown Resolver
IRemUnknown2 IRemUnknown2 Resolver
ISDN
ISDN Q.921-User Adaptation Layer
ISDN User Part
ISO 10589 ISIS InTRA Domain Routeing Information Exchange Protocol
ISO 8073 COTP Connection-Oriented Transport Protocol
ISO 8327-1 OSI Session Protocol
ISO 8473 CLNP ConnectionLess Network Protocol
ISO 8602 CLTP ConnectionLess Transport Protocol
ISO 8823 OSI Presentation Protocol
ISO 9542 ESIS Routeing Information Exchange Protocol
ISystemActivator ISystemActivator Resolver
ITU-T E.164 number
ITU-T Recommendation H.261
ITU-T Recommendation H.263 RTP Payload header (RFC2190)
InMon sFlow
Information Access Protocol
Intel ANS probe
Intelligent Platform Management Interface
Inter-Access-Point Protocol
Inter-Asterisk eXchange v2
InterSwitch Message Protocol
Interbase
Internet Cache Protocol
Internet Communications Engine Protocol
Internet Content Adaptation Protocol
Internet Control Message Protocol
Internet Control Message Protocol v6
Internet Group Management Protocol
Internet Group membership Authentication Protocol
Internet Message Access Protocol
Internet Printing Protocol
Internet Protocol
Internet Protocol Version 6
Internet Relay Chat
Internet Security Association and Key Management Protocol
Internetwork Packet eXchange
IrCOMM Protocol
IrDA Link Access Protocol
IrDA Link Management Protocol
JPEG File Interchange Format
Jabber XML Messaging
Java RMI
Java Serialization
Kerberos
Kerberos Administration
Kerberos v4
Kernel Lock Manager
LWAP Control Message
LWAPP Encapsulated Packet
LWAPP Layer 3 Packet
Label Distribution Protocol
Laplink
Layer 2 Tunneling Protocol
Light Weight DNS RESolver (BIND9)
Lightweight Directory Access Protocol
Line Printer Daemon Protocol
Line-based text data
Link Access Procedure Balanced (LAPB)
Link Access Procedure Balanced Ethernet (LAPBETHER)
Link Access Procedure, Channel D (LAPD)
Link Aggregation Control Protocol
Link Management Protocol (LMP)
Linux cooked-mode capture
Local Management Interface
LocalTalk Link Access Protocol
Log Message
Logical Link Control GPRS
Logical-Link Control
Lucent/Ascend debug output
MAC Control
MDS Header
MEGACO
MIME Multipart Media Encapsulation
MMS Message Encapsulation
MS Kpasswd
MS Proxy Protocol
MSN Messenger Service
MSNIP: Multicast Source Notification of Interest Protocol
MTP 2 Transparent Proxy
MTP 2 User Adaptation Layer
MTP 3 User Adaptation Layer
MTP2 Peer Adaptation Layer
Media Gateway Control Protocol
Media Type
Media Type: message/http
Message Transfer Part Level 2
Message Transfer Part Level 3
Message Transfer Part Level 3 Management
Microsoft Directory Replication Service
Microsoft Distributed File System
Microsoft Distributed Link Tracking Server Service
Microsoft Encrypted File System Service
Microsoft Eventlog Service
Microsoft Exchange MAPI
Microsoft File Replication Service
Microsoft File Replication Service API
Microsoft Local Security Architecture
Microsoft Local Security Architecture (Directory Services)
Microsoft Messenger Service
Microsoft Network Logon
Microsoft Registry
Microsoft Security Account Manager
Microsoft Server Service
Microsoft Service Control
Microsoft Spool Subsystem
Microsoft Task Scheduler Service
Microsoft Telephony API Service
Microsoft Windows Browser Protocol
Microsoft Windows Lanman Remote API Protocol
Microsoft Windows Logon Protocol
Microsoft Workstation Service
Mobile IP
Mobile IPv6
Modbus/TCP
Mount Service
MultiProtocol Label Switching Header
Multicast Router DISCovery protocol
Multicast Source Discovery Protocol
Multiprotocol Label Switching Echo
MySQL Protocol
NFSACL
NFSAUTH
NIS+
NIS+ Callback
NSPI
NTLM Secure Service Provider
Name Binding Protocol
Name Management Protocol over IPX
NetBIOS
NetBIOS Datagram Service
NetBIOS Name Service
NetBIOS Session Service
NetBIOS over IPX
NetScape Certificate Extensions
NetWare Core Protocol
NetWare Link Services Protocol
NetWare Serialization Protocol
Network Data Management Protocol
Network File System
Network Lock Manager Protocol
Network News Transfer Protocol
Network Status Monitor CallBack Protocol
Network Status Monitor Protocol
Network Time Protocol
Nortel SONMP
Novell Distributed Print System
Novell Modular Authentication Service
Null/Loopback
OSI ISO 8571 FTAM Protocol
OSI ISO/IEC 10035-1 ACSE Protocol
Open Policy Service Interface
Open Shortest Path First
OpenBSD Encapsulating device
OpenBSD Packet Filter log file
OpenBSD Packet Filter log file, pre 3.4
Optimized Link State Routing Protocol
PC NFS
PKCS#1
PKINIT
PKIX1Explitit
PKIX1Implitit
POSTGRESQL
PPP Bandwidth Allocation Control Protocol
PPP Bandwidth Allocation Protocol
PPP CDP Control Protocol
PPP Callback Control Protocol
PPP Challenge Handshake Authentication Protocol
PPP Compressed Datagram
PPP Compression Control Protocol
PPP IP Control Protocol
PPP IPv6 Control Protocol
PPP Link Control Protocol
PPP MPLS Control Protocol
PPP Multilink Protocol
PPP Multiplexing
PPP OSI Control Protocol
PPP Password Authentication Protocol
PPP VJ Compression
PPP-over-Ethernet Discovery
PPP-over-Ethernet Session
PPPMux Control Protocol
Packed Encoding Rules (ASN.1 X.691)
Packet Cable Lawful Intercept
PacketCable
Point-to-Point Protocol
Point-to-Point Tunnelling Protocol
Port Aggregation Protocol
Portmap
Post Office Protocol
Pragmatic General Multicast
Precision Time Protocol (IEEE1588)
Prism
Privilege Server operations
Protocol Independent Multicast
Q.2931
Q.931
Q.933
Quake II Network Protocol
Quake III Arena Network Protocol
Quake Network Protocol
QuakeWorld Network Protocol
Qualified Logical Link Control
RDM
RFC 2250 MPEG1
RFC 2833 RTP Event
RIPng
RPC Browser
RS Interface properties
RSTAT
RSYNC File Synchroniser
RTNET
RTcfg
RX Protocol
Radio Access Network Application Part
Radius Protocol
Raw packet data
Real Time Streaming Protocol
Real-Time Publish-Subscribe Wire Protocol
Real-Time Transport Protocol
Real-time Transport Control Protocol
Redundant Link Management Protocol
Registry Server Attributes Manipulation Interface
Registry server administration operations.
Reliable UDP
Remote Management Control Protocol
Remote Override interface
Remote Procedure Call
Remote Program Load
Remote Quota
Remote Shell
Remote Shutdown
Remote Wall protocol
Remote sec_login preauth interface.
Resource ReserVation Protocol (RSVP)
Rlogin Protocol
Routing Information Protocol
Routing Table Maintenance Protocol
SADMIND
SCSI
SEBEK - Kernel Data Capture
SGI Mount Service
SMB (Server Message Block Protocol)
SMB MailSlot Protocol
SMB Pipe Protocol
SNA-over-Ethernet
SNMP Multiplex Protocol
SPNEGO-KRB5
SPRAY
SS7 SCCP-User Adaptation Layer
SSCOP
SSH Protocol
Secure Socket Layer
Sequenced Packet eXchange
Serial Infrared
Service Advertisement Protocol
Service Location Protocol
Session Announcement Protocol
Session Description Protocol
Session Initiation Protocol
Session Initiation Protocol (SIP as raw text)
Short Message Peer to Peer
Signaling Compression
Signalling Connection Control Part
Signalling Connection Control Part Management
Simple Mail Transfer Protocol
Simple Network Management Protocol
Simple Traversal of UDP Through NAT
Sinec H1 Protocol
Sipfrag
Skinny Client Control Protocol
SliMP3 Communication Protocol
Socks Protocol
SoulSeek Protocol
Spanning Tree Protocol
Spnego
Stream Control Transmission Protocol
Subnetwork Dependent Convergence Protocol
Symantec Enterprise Firewall
Synchronous Data Link Control (SDLC)
Syslog message
Systems Network Architecture
Systems Network Architecture XID
T38
TACACS
TACACS+
TEI Management Procedure, Channel D (LAPD)
TPKT
Tabular Data Stream
Tazmen Sniffer Protocol
Telnet
Teredo IPv6 over UDP tunneling
Time Protocol
Time Synchronization Protocol
Tiny Transport Protocol
Token-Ring
Token-Ring Media Access Control
Transaction Capabilities Application Part
Transmission Control Protocol
Transparent Network Substrate Protocol
Transport Adapter Layer Interface v1.0, RFC 3094
Trivial File Transfer Protocol
UDP Encapsulation of IPsec Packets
Universal Computer Protocol
User Datagram Protocol
V5.2-User Adaptation Layer
Virtual Router Redundancy Protocol
Virtual Trunking Protocol
WAP Binary XML
WAP Session Initiation Request
Web Cache Coordination Protocol
WebSphere MQ
WebSphere MQ Programmable Command Formats
Wellfleet Breath of Life
Wellfleet Compression
Wellfleet HDLC
Who
Windows 2000 DNS
Wireless Session Protocol
Wireless Transaction Protocol
Wireless Transport Layer Security
X Display Manager Control Protocol
X.25
X.25 over TCP
X.29
X.509 Authentication Framework
X.509 Certificate Extensions
X.509 Information Framework
X.509 Selected Attribute Types
X11
Xyplex
Yahoo Messenger Protocol
Yahoo YMSG Messenger Protocol
Yellow Pages Bind
Yellow Pages Passwd
Yellow Pages Service
Yellow Pages Transfer
Zebra Protocol
Zone Information Protocol
eDonkey Protocol
giFT Internet File Transfer
iSCSI
iSNS
Q 1.6: Are there any plans to support {your favorite protocol}?
A: Support for particular protocols is added to Ethereal as a result
of people contributing that support; no formal plans for adding
support for particular protocols in particular future releases exist.
Q 1.7: Can Ethereal read capture files from {your favorite network
analyzer}?
A: Support for particular protocols is added to Ethereal as a result
of people contributing that support; no formal plans for adding
support for particular protocols in particular future releases exist.
If a network analyzer writes out files in a format already supported
by Ethereal (e.g., in libpcap format), Ethereal may already be able to
read them, unless the analyzer has added its own proprietary
extensions to that format.
If a network analyzer writes out files in its own format, or has added
proprietary extensions to another format, in order to make Ethereal
read captures from that network analyzer, we would either have to have
a specification for the file format, or the extensions, sufficient to
give us enough information to read the parts of the file relevant to
Ethereal, or would need at least one capture file in that format AND a
detailed textual analysis of the packets in that capture file (showing
packet time stamps, packet lengths, and the top-level packet header)
in order to reverse-engineer the file format.
Note that there is no guarantee that we will be able to
reverse-engineer a capture file format.
Q 1.8: What devices can Ethereal use to capture packets?
A: Ethereal can read live data from Ethernet, Token-Ring, FDDI, serial
(PPP and SLIP) (if the OS on which it's running allows Ethereal to do
so), 802.11 wireless LAN (if the OS on which it's running allows
Ethereal to do so), ATM connections (if the OS on which it's running
allows Ethereal to do so), and the "any" device supported on Linux by
recent versions of libpcap. See the list of supported capture media on
various OSes for details (several items in there say "Unknown", which
doesn't mean "Ethereal can't capture on them", it means "we don't know
whether it can capture on them"; we expect that it will be able to
capture on many of them, but we haven't tried it ourselves - if you
try one of those types and it works, please send an update to
_EWEB_MAILTO).
It can also read a variety of capture file formats, including:
* libpcap/tcpdump
* Sun snoop/atmsnoop
* Shomiti/Finisar Surveyor
* LanAlyzer
* DOS-based Sniffer (compressed and uncompressed)
* MS Network Monitor
* AIX iptrace
* NetXray and Windows-based Sniffer
* EtherPeek/TokenPeek/AiroPeek
* RADCOM WAN/LAN analyzer
* Lucent/Ascend debug output
* Toshiba ISDN router "snoop" output
* HPUX nettl
* ISDN4BSD "i4btrace" utility.
* Cisco Secure IDS
* pppd log files (pppdump format)
* VMS TCPIPtrace
* DBS Etherwatch
* Visual Networks' Visual UpTime
* CoSine L2 debug
so that it can read traces from various network types, as captured by
other applications or equipment, even if it cannot itself capture on
those network types.
Q 1.9: How do you pronounce Ethereal? Where did the name come from?
A: The English pronunciation can be found in Merriam-Webster's online
dictionary at
http://www.m-w.com/cgi-bin/dictionary?book=Dictionary&va=ethereal.
According to the book "Computer Networks" by Andrew Tannenbaum,
Ethernet was named after the "luminiferous ether" which was once
thought to carry electromagnetic radiation. Taking that into
consideration, Ethereal seemed like an appropriate name for something
that started out as an Ethernet analyzer.
Downloading Ethereal
Q 2.1: I downloaded the Win32 installer, but when I try to run it, I
get an error.
A: The program you used to download it may have downloaded it
incorrectly. Web browsers sometimes may do this.
Try downloading it with, for example:
* Wget, for which Windows binaries are available on the SunSITE FTP
server at sunsite.tk or Heiko Herold's windows wget spot - wGetGUI
offers a GUI interface that uses wget;
* WS_FTP from Ipswitch,
* the ftp command that comes with Windows.
If you use the ftp command, make sure you do the transfer in binary
mode rather than ASCII mode, by using the binary command before
transferring the file.
Q 2.2: When I try to download the WinPcap driver and library, I can't
get to the WinPcap Web site.
A: As is the case with all Web sites, that site won't necessarily
always be accessible; the server may be down due to a problem or down
for maintenance, or there may be a networking problem between you and
the server. You should try again later, or try the local mirror or the
Wiretapped.net mirror.
Installing Ethereal
Q 3.1: I installed an Ethereal RPM, but Ethereal doesn't seem to be
installed; only Tethereal is installed.
A: Older versions of the Red Hat RPMs for Ethereal put only the
non-GUI components into the ethereal RPM, the fact that Ethereal is a
GUI program nonwithstanding; newer versions make it a bit clearer by
giving that RPM a name starting with ethereal-base.
In those older versions, there's a separate ethereal-gnome RPM that
includes GUI components such as Ethereal itself, the fact that
Ethereal doesn't use GNOME nonwithstanding; newer versions make it a
bit clearer by giving that RPM a name starting with ethereal-gtk+.
Find the ethereal-gnome or ethereal-gtk+ RPM, and install that also.
Building Ethereal
Q 4.1: The configure script can't find pcap.h or bpf.h, but I have
libpcap installed.
A: Are you sure pcap.h and bpf.h are installed? The official
distribution of libpcap only installs the libpcap.a library file when
"make install" is run. To install pcap.h and bpf.h, you must run "make
install-incl". If you're running Debian or Redhat, make sure you have
the "libpcap-dev" or "libpcap-devel" packages installed.
It's also possible that pcap.h and bpf.h have been installed in a
strange location. If this is the case, you may have to tweak
aclocal.m4.
Q 4.2: Why do I get the error
dftest_DEPENDENCIES was already defined in condition TRUE, which
implies condition HAVE_PLUGINS_TRUE
when I try to build Ethereal from SVN or a SVN snapshot?
A: You probably have automake 1.5 installed on your machine (the
command automake --version will report the version of automake on your
machine). There is a bug in that version of automake that causes this
problem; upgrade to a later version of automake (1.6 or later).
Q 4.3: The link fails with a number of "Output line too long."
messages followed by linker errors.
A: The version of the sed command on your system is incapable of
handling very long lines. On Solaris, for example, /usr/bin/sed has a
line length limit too low to allow libtool to work; /usr/xpg4/bin/sed
can handle it, as can GNU sed if you have it installed.
On Solaris, changing your command search path to search /usr/xpg4/bin
before /usr/bin should make the problem go away; on any platform on
which you have this problem, installing GNU sed and changing your
command path to search the directory in which it is installed before
searching the directory with the version of sed that came with the OS
should make the problem go away.
Q 4.4: The link fails on Solaris because plugin_list is undefined.
A: This appears to be due to a problem with some versions of the GTK+
and GLib packages from www.sunfreeware.org; un-install those packages,
and try getting the 1.2.10 versions from that site, or the versions
from The Written Word, or the versions from Sun's GNOME distribution,
or the versions from the supplemental software CD that comes with the
Solaris media kit, or build them from source from the GTK Web site.
Then re-run the configuration script, and try rebuilding Ethereal. (If
you get the 1.2.10 versions from www.sunfreeware.org, and the problem
persists, un-install them and try installing one of the other versions
mentioned.)
Q 4.5: The build fails on Windows because of conflicts between
winsock.h and winsock2.h.
A: As of Ethereal 0.9.5, you must install WinPcap 2.3 or later, and
the corresponding version of the developer's pack, in order to be able
to compile Ethereal; it will not compile with older versions of the
developer's pack. The symptoms of this failure are conflicts between
definitions in winsock.h and in winsock2.h; Ethereal uses winsock2.h,
but pre-2.3 versions of the WinPcap developer's packet use winsock.h.
(2.3 uses winsock2.h, so if Ethereal were to use winsock.h, it would
not be able to build with current versions of the WinPcap developer's
pack.)
Note that the installed version of the developer's pack should be the
same version as the version of WinPcap you have installed.
Using Ethereal
Q 5.1: When I use Ethereal to capture packets, I see only packets to
and from my machine, or I'm not seeing all the traffic I'm expecting
to see from or to the machine I'm trying to monitor.
A: This might be because the interface on which you're capturing is
plugged into a switch; on a switched network, unicast traffic between
two ports will not necessarily appear on other ports - only broadcast
and multicast traffic will be sent to all ports.
Note that even if your machine is plugged into a hub, the "hub" may be
a switched hub, in which case you're still on a switched network.
Note also that on the Linksys Web site, they say that their
auto-sensing hubs "broadcast the 10Mb packets to the port that operate
at 10Mb only and broadcast the 100Mb packets to the ports that operate
at 100Mb only", which would indicate that if you sniff on a 10Mb port,
you will not see traffic coming sent to a 100Mb port, and vice versa.
This problem has also been reported for Netgear dual-speed hubs, and
may exist for other "auto-sensing" or "dual-speed" hubs.
Some switches have the ability to replicate all traffic on all ports
to a single port so that you can plug your analyzer into that single
port to sniff all traffic. You would have to check the documentation
for the switch to see if this is possible and, if so, to see how to do
this. See the switch reference page on the Ethereal Wiki for
information on some switches. (Note that it's a Wiki, so you can
update or fix that information, or add additional information on those
switches or information on new switches, yourself.)
Note also that many firewall/NAT boxes have a switch built into them;
this includes many of the "cable/DSL router" boxes. If you have a box
of that sort, that has a switch with some number of Ethernet ports
into which you plug machines on your network, and another Ethernet
port used to connect to a cable or DSL modem, you can, at least, sniff
traffic between the machines on your network and the Internet by
plugging the Ethernet port on the router going to the modem, the
Ethernet port on the modem, and the machine on which you're running
Ethereal into a hub (make sure it's not a switching hub, and that, if
it's a dual-speed hub, all three of those ports are running at the
same speed.
If your machine is not plugged into a switched network or a dual-speed
hub, or it is plugged into a switched network but the port is set up
to have all traffic replicated to it, the problem might be that the
network interface on which you're capturing doesn't support
"promiscuous" mode, or because your OS can't put the interface into
promiscuous mode. Normally, network interfaces supply to the host
only:
* packets sent to one of that host's link-layer addresses;
* broadcast packets;
* multicast packets sent to a multicast address that the host has
configured the interface to accept.
Most network interfaces can also be put in "promiscuous" mode, in
which they supply to the host all network packets they see. Ethereal
will try to put the interface on which it's capturing into promiscuous
mode unless the "Capture packets in promiscuous mode" option is turned
off in the "Capture Options" dialog box, and Tethereal will try to put
the interface on which it's capturing into promiscuous mode unless the
-p option was specified. However, some network interfaces don't
support promiscuous mode, and some OSes might not allow interfaces to
be put into promiscuous mode.
If the interface is not running in promiscuous mode, it won't see any
traffic that isn't intended to be seen by your machine. It will see
broadcast packets, and multicast packets sent to a multicast MAC
address the interface is set up to receive.
You should ask the vendor of your network interface whether it
supports promiscuous mode. If it does, you should ask whoever supplied
the driver for the interface (the vendor, or the supplier of the OS
you're running on your machine) whether it supports promiscuous mode
with that network interface.
In the case of token ring interfaces, the drivers for some of them, on
Windows, may require you to enable promiscuous mode in order to
capture in promiscuous mode. Ask the vendor of the card how to do
this, or see, for example, this information on promiscuous mode on
some Madge token ring adapters (note that those cards can have
promiscuous mode disabled permanently, in which case you can't enable
it).
In the case of wireless LAN interfaces, it appears that, when those
interfaces are promiscuously sniffing, they're running in a
significantly different mode from the mode that they run in when
they're just acting as network interfaces (to the extent that it would
be a significant effor for those drivers to support for promiscuously
sniffing and acting as regular network interfaces at the same time),
so it may be that Windows drivers for those interfaces don't support
promiscuous mode.
Q 5.2: I can't see any TCP packets other than packets to and from my
machine, even though another analyzer on the network sees those
packets.
A: You're probably not seeing any packets other than unicast packets
to or from your machine, and broadcast and multicast packets; a switch
will normally send to a port only unicast traffic sent to the MAC
address for the interface on that port, and broadcast and multicast
traffic - it won't send to that port unicast traffic sent to a MAC
address for some other interface - and a network interface not in
promiscuous mode will receive only unicast traffic sent to the MAC
address for that interface, broadcast traffic, and multicast traffic
sent to a multicast MAC address the interface is set up to receive.
TCP doesn't use broadcast or multicast, so you will only see your own
TCP traffic, but UDP services may use broadcast or multicast so you'll
see some UDP traffic - however, this is not a problem with TCP
traffic, it's a problem with unicast traffic, as you also won't see
all UDP traffic between other machines.
I.e., this is probably the same question as this earlier one; see the
response to that question.
Q 5.3: I'm only seeing ARP packets when I try to capture traffic.
A: You're probably on a switched network, and running Ethereal on a
machine that's not sending traffic to the switch and not being sent
any traffic from other machines on the switch. ARP packets are often
broadcast packets, which are sent to all switch ports.
I.e., this is probably the same question as this earlier one; see the
response to that question.
Q 5.4: I'm running Ethereal on Windows; why does some network
interface on my machine not show up in the list of interfaces in the
"Interface:" field in the dialog box popped up by "Capture->Start",
and/or why does Ethereal give me an error if I try to capture on that
interface?
A: If you are running Ethereal on Windows NT 4.0, Windows 2000,
Windows XP, or Windows Server, and this is the first time you have run
a WinPcap-based program (such as Ethereal, or Tethereal, or WinDump,
or Analyzer, or...) since the machine was rebooted, you need to run
that program from an account with administrator privileges; once you
have run such a program, you will not need administrator privileges to
run any such programs until you reboot.
If you are running on Windows 95/98/Me, or if you are running on
Windows NT 4.0/2000/XP/Server and have administrator privileges or a
WinPcap-based program has been run with those privileges since the
machine rebooted, then note that Ethereal relies on the WinPcap
library, on the WinPcap device driver, and on the facilities that come
with the OS on which it's running in order to do captures.
Therefore, if the OS, the WinPcap library, or the WinPcap driver don't
support capturing on a particular network interface device, Ethereal
won't be able to capture on that device.
Note that:
1. 2.02 and earlier versions of the WinPcap driver and library that
Ethereal uses for packet capture didn't support Token Ring
interfaces; versions 2.1 and later support Token Ring, and the
current version of Ethereal works with (and, in fact, requires)
WinPcap 2.1 or later.
If you are having problems capturing on Token Ring interfaces, and
you have WinPcap 2.02 or an earlier version of WinPcap installed,
you should uninstall WinPcap, download and install the current
version of WinPcap, and then install the latest version of
Ethereal.
2. On Windows 95, 98, or Me, sometimes more than one interface will
be given the same name; if that is the case, you will only be able
to capture on one of those interfaces - it's not clear to which
one the name, when used in a WinPcap-based application, will
refer. For example, if you have a PPP serial interface and a VPN
interface, they might show up with the same name, for example
"ppp-mac", and if you try to capture on "ppp-mac", it might not
capture on the interface you're currently using. In that case, you
might, for example, have to remove the VPN interface from the
system in order to capture on the PPP serial interface.
3. WinPcap 3.0 doesn't support PPP WAN interfaces, and WinPcap 2.3
doesn't support PPP WAN interfaces on Windows NT/2000/XP/Server,
so Ethereal cannot capture packets on those devices with WinPcap
3.0, or with WInPcap 2.x when running on Windows
NT/2000/XP/Server. Regular dial-up lines, ISDN lines, and various
other lines such as T1/E1 lines are all PPP interfaces. This may
cause the interface not to show up on the list of interfaces in
the "Capture Options" dialog.
4. WinPcap prior to 3.0 does not support multiprocessor machines
(note that machines with a single multi-threaded processor, such
as Intel's new multi-threaded x86 processors, are multiprocessor
machines as far as the OS and WinPcap are concerned), and recent
2.x versions of WinPcap refuse to operate if they detect that
they're running on a multiprocessor machine, which means that they
may not show any network interfaces. You will need to use WinPcap
3.0 to capture on a multiprocessor machine.
If an interface doesn't show up in the list of interfaces in the
"Interface:" field, and you know the name of the interface, try
entering that name in the "Interface:" field and capturing on that
device.
If the attempt to capture on it succeeds, the interface is somehow not
being reported by the mechanism Ethereal uses to get a list of
interfaces. Try listing the interfaces with WinDump; see the WinDump
Web site or the local mirror of the WinDump Web site for information
on using WinDump.
You would run WinDump with the -D flag; if it lists the interface,
please report this to ethereal-dev@ethereal.com giving full details of
the problem, including
* the operating system you're using, and the version of that
operating system;
* the type of network device you're using;
* the output of WinDump.
If WinDump does not list the interface, this is almost certainly a
problem with one or more of:
* the operating system you're using;
* the device driver for the interface you're using;
* the WinPcap library and/or the WinPcap device driver;
so first check the WinPcap FAQ, the local mirror of that FAQ, or the
Wiretapped.net mirror of that FAQ, to see if your problem is mentioned
there. If not, then see the WinPcap support page (or the local mirror
of that page) - check the "Submitting bugs" section.
If you are having trouble capturing on a particular network interface,
first try capturing on that device with WinDump; see the WinDump Web
site or the local mirror of the WinDump Web site for information on
using WinDump.
If you can capture on the interface with WinDump, send mail to
ethereal-users@ethereal.com giving full details of the problem,
including
* the operating system you're using, and the version of that
operating system;
* the type of network device you're using;
* the error message you get from Ethereal.
If you cannot capture on the interface with WinDump, this is almost
certainly a problem with one or more of:
* the operating system you're using;
* the device driver for the interface you're using;
* the WinPcap library and/or the WinPcap device driver;
so first check the WinPcap FAQ, the local mirror of that FAQ, or the
Wiretapped.net mirror of that FAQ, to see if your problem is mentioned
there. If not, then see the WinPcap support page (or the local mirror
of that page) - check the "Submitting bugs" section.
You may also want to ask the ethereal-users@ethereal.com and the
winpcap-users@winpcap.polito.it mailing lists to see if anybody
happens to know about the problem and know a workaround or fix for the
problem. (Note that you will have to subscribe to that list in order
to be allowed to mail to it; see the WinPcap support page, or the
local mirror of that page, for information on the mailing list.) In
your mail, please give full details of the problem, as described
above, and also indicate that the problem occurs with WinDump, not
just with Ethereal.
Q 5.5: I'm running Ethereal on Windows; why do no network interfaces
show up in the list of interfaces in the "Interface:" field in the
dialog box popped up by "Capture->Start"?
A: This is really the same question as the previous one; see the
response to that question.
Q 5.6: I'm running Ethereal on Windows; why doesn't my serial
port/ADSL modem/ISDN modem/show up in the list of interfaces in the
"Interface:" field in the dialog box popped up by "Capture->Start"?
A: All of those devices support Internet access using the
Point-to-Point (PPP) protocol; WinPcap 3.0 doesn't support PPP
interfaces, and WinPcap 2.x doesn't support PPP interfaces on Windows
NT/2000/XP/Server, so Ethereal cannot capture packets on those devices
with WinPcap 3.0, or with WinPcap 2.x when running on Windows
NT/2000/XP/Server. This may cause the interface not to show up on the
list of interfaces in the "Capture Options" dialog.
Q 5.7: I'm running Ethereal on a UNIX-flavored OS; why does some
network interface on my machine not show up in the list of interfaces
in the "Interface:" field in the dialog box popped up by
"Capture->Start", and/or why does Ethereal give me an error if I try
to capture on that interface?
A: You may need to run Ethereal from an account with sufficient
privileges to capture packets, such as the super-user account. Only
those interfaces that Ethereal can open for capturing show up in that
list; if you don't have sufficient privileges to capture on any
interfaces, no interfaces will show up in the list.
If you are running Ethereal from an account with sufficient
privileges, then note that Ethereal relies on the libpcap library, and
on the facilities that come with the OS on which it's running in order
to do captures.
Therefore, if the OS or the libpcap library don't support capturing on
a particular network interface device, Ethereal won't be able to
capture on that device.
On Linux, note that you need to have "packet socket" support enabled
in your kernel; see the "Packet socket" item in the Linux
"Configure.help" file.
On BSD, note that you need to have BPF support enabled in your kernel;
see the documentation for your system for information on how to enable
BPF support (if it's not enabled by default on your system).
On DEC OSF/1, Digital UNIX, or Tru64 UNIX, note that you need to have
packet filtering support in your kernel; the doconfig command will
allow you to configure and build a new kernel with that option.
On Solaris, note that libpcap 0.6.2 and earlier didn't support Token
Ring interfaces; the current version, 0.7.2, does support Token Ring,
and the current version of Ethereal works with libcap 0.7.2 and later.
If an interface doesn't show up in the list of interfaces in the
"Interface:" field, and you know the name of the interface, try
entering that name in the "Interface:" field and capturing on that
device.
If the attempt to capture on it succeeds, the interface is somehow not
being reported by the mechanism Ethereal uses to get a list of
interfaces; please report this to ethereal-dev@ethereal.com giving
full details of the problem, including
* the operating system you're using, and the version of that
operating system (for Linux, give both the version number of the
kernel and the name and version number of the distribution you're
using);
* the type of network device you're using.
If you are having trouble capturing on a particular network interface,
and you've made sure that (on platforms that require it) you've
arranged that packet capture support is present, as per the above,
first try capturing on that device with tcpdump.
If you can capture on the interface with tcpdump, send mail to
ethereal-users@ethereal.com giving full details of the problem,
including
* the operating system you're using, and the version of that
operating system (for Linux, give both the version number of the
kernel and the name and version number of the distribution you're
using);
* the type of network device you're using;
* the error message you get from Ethereal.
If you cannot capture on the interface with tcpdump, this is almost
certainly a problem with one or more of:
* the operating system you're using;
* the device driver for the interface you're using;
* the libpcap library;
so you should report the problem to the company or organization that
produces the OS (in the case of a Linux distribution, report the
problem to whoever produces the distribution).
You may also want to ask the ethereal-users@ethereal.com and the
tcpdump-workers@tcpdump.org mailing lists to see if anybody happens to
know about the problem and know a workaround or fix for the problem.
In your mail, please give full details of the problem, as described
above, and also indicate that the problem occurs with tcpdump not just
with Ethereal.
Q 5.8: I'm running Ethereal on a UNIX-flavored OS; why do no network
interfaces show up in the list of interfaces in the "Interface:" field
in the dialog box popped up by "Capture->Start"?
A: This is really the same question as the previous one; see the
response to that question.
Q 5.9: Can Ethereal capture on (my T1/E1 line, SS7 links, etc.)?
A: Ethereal can only capture on devices supported by libpcap/WinPcap.
On most OSes, only devices that can act as network interfaces of the
type that support IP are supported as capture devices for
libpcap/WinPcap, although the device doesn't necessarily have to be
running as an IP interface in order to support traffic capture.
On Linux and FreeBSD, libpcap 0.8 and later support the API for Endace
Measurement Systems' DAG cards, so that a system with one of those
cards, and its driver and libraries, installed can capture traffic
with those cards with libpcap-based applications. You would either
have to have a version of Ethereal built with that version of libpcap,
or a dynamically-linked version of Ethereal and a shared libpcap
library with DAG support, in order to do so with Ethereal. You should
ask Endace whether that could be used to capture traffic on, for
example, your T1/E1 link.
There is currently no hardware to support capturing on SS7 links with
libpcap. (Note that the fact that Ethereal includes dissectors for
many SS7 protocols doesn't imply that it can capture traffic from SS7
links; those protocols can be run over Internet protocols.)
Q 5.10: How do I put an interface into promiscuous mode?
A: By not disabling promiscuous mode when running Ethereal or
Tethereal.
Note, however, that:
* the form of promiscuous mode that libpcap (the library that
programs such as tcpdump, Ethereal, etc. use to do packet capture)
turns on will not necessarily be shown if you run ifconfig on the
interface on a UNIX system;
* some network interfaces might not support promiscuous mode, and
some drivers might not allow promiscuous mode to be turned on -
see this earlier question for more information on that;
* the fact that you're not seeing any traffic, or are only seeing
broadcast traffic, or aren't seeing any non-broadcast traffic
other than traffic to or from the machine running Ethereal, does
not mean that promiscuous mode isn't on - see this earlier
question for more information on that.
I.e., this is probably the same question as this earlier one; see the
response to that question.
Q 5.11: I can set a display filter just fine, but capture filters
don't work.
A: Capture filters currently use a different syntax than display
filters. Here's the corresponding section from the ethereal(1) man
page:
"Display filters in Ethereal are very powerful; more fields are
filterable in Ethereal than in other protocol analyzers, and the
syntax you can use to create your filters is richer. As Ethereal
progresses, expect more and more protocol fields to be allowed in
display filters.
Packet capturing is performed with the pcap library. The capture
filter syntax follows the rules of the pcap library. This syntax is
different from the display filter syntax."
The capture filter syntax used by libpcap can be found in the
tcpdump(8) man page.
Q 5.12: I'm entering valid capture filters, but I still get "parse
error" errors.
A: There is a bug in some versions of libpcap/WinPcap that cause it to
report parse errors even for valid expressions if a previous filter
expression was invalid and got a parse error.
Try exiting and restarting Ethereal; if you are using a version of
libpcap/WinPcap with this bug, this will "erase" its memory of the
previous parse error. If the capture filter that got the "parse error"
now works, the earlier error with that filter was probably due to this
bug.
The bug was fixed in libpcap 0.6; 0.4[.x] and 0.5[.x] versions of
libpcap have this bug, but 0.6[.x] and later versions don't.
Versions of WinPcap prior to 2.3 are based on pre-0.6 versions of
libpcap, and have this bug; WinPcap 2.3 is based on libpcap 0.6.2, and
doesn't have this bug.
If you are running Ethereal on a UNIX-flavored platform, run "ethereal
-v", or select "About Ethereal..." from the "Help" menu in Ethereal,
to see what version of libpcap it's using. If it's not 0.6 or later,
you will need either to upgrade your OS to get a later version of
libpcap, or will need to build and install a later version of libpcap
from the tcpdump.org Web site and then recompile Ethereal from source
with that later version of libpcap.
If you are running Ethereal on Windows with a pre-2.3 version of
WinPcap, you will need to un-install WinPcap and then download and
install WinPcap 2.3.
Q 5.13: I saved a filter and tried to use its name to filter the
display, but I got an "Unexpected end of filter string" error.
A: You cannot use the name of a saved display filter as a filter. To
filter the display, you can enter a display filter expression - not
the name of a saved display filter - in the "Filter:" box at the
bottom of the display, and type the key or press the "Apply" button
(that does not require you to have a saved filter), or, if you want to
use a saved filter, you can press the "Filter:" button, select the
filter in the dialog box that pops up, and press the "OK" button.
Q 5.14: Why am I seeing lots of packets with incorrect TCP checksums?
A: If the packets that have incorrect TCP checksums are all being sent
by the machine on which Ethereal is running, this is probably because
the network interface on which you're capturing does TCP checksum
offloading. That means that the TCP checksum is added to the packet by
the network interface, not by the OS's TCP/IP stack; when capturing on
an interface, packets being sent by the host on which you're capturing
are directly handed to the capture interface by the OS, which means
that they are handed to the capture interface without a TCP checksum
being added to them.
The only way to prevent this from happening would be to disable TCP
checksum offloading, but
1. that might not even be possible on some OSes;
2. that could reduce networking performance significantly.
However, you can disable the check that Ethereal does of the TCP
checksum, so that it won't report any packets as having TCP checksum
errors, and so that it won't refuse to do TCP reassembly due to a
packet having an incorrect TCP checksum. That can be set as an
Ethereal preference by selecting "Preferences" from the "Edit" menu,
opening up the "Protocols" list in the left-hand pane of the
"Preferences" dialog box, selecting "TCP", from that list, turning off
the "Check the validity of the TCP checksum when possible" option,
clicking "Save" if you want to save that setting in your preference
file, and clicking "OK".
It can also be set on the Ethereal or Tethereal command line with a -o
tcp.check_checksum:false command-line flag, or manually set in your
preferences file by adding a tcp.check_checksum:false line.
Q 5.15: I've just installed Ethereal, and the traffic on my local LAN
is boring.
A: We have a collection of strange and exotic sample capture files at
http://www.ethereal.com/sample/
Q 5.16: When I run Ethereal on Solaris 8, it dies with a Bus Error
when I start it.
A: Some versions of the GTK+ library from www.sunfreeware.org appear
to be buggy, causing Ethereal to drop core with a Bus Error.
Un-install those packages, and try getting the 1.2.10 version from
that site, or the version from The Written Word, or the version from
Sun's GNOME distribution, or the version from the supplemental
software CD that comes with the Solaris media kit, or build it from
source from the GTK Web site. Update the GLib library to the 1.2.10
version, from the same source, as well. (If you get the 1.2.10
versions from www.sunfreeware.org, and the problem persists,
un-install them and try installing one of the other versions
mentioned.)
Similar problems may exist with older versions of GTK+ for earlier
versions of Solaris.
Q 5.17: When I run Ethereal, I get an error
Gtk-CRITICAL **: file gtkwindow.c: line 3107 (gtk_window_resize):
assertion `height > 0' failed.
A: This is a bug in Ethereal 0.10.5 and 0.10.5a, which is fixed in
Ethereal 0.10.6 and later releases.
Q 5.18: When I run Tethereal with the "-x" option, it crashes with an
error
"** ERROR **: file print.c: line 691 (print_line): should not be
reached.
A: This is a bug in Ethereal 0.10.0a, which is fixed in 0.10.1 and
later releases. To work around the bug, don't use "-x" unless you're
also using "-V"; note that "-V" produces a full dissection of each
packet, so you might not want to use it.
To get a fixed version, either build the current SVN version from
anonymous SVN or a nightly SVN snapshot, or apply to tethereal.c in
the 0.10.0a source tarball the changes between the broken and the
fixed versions, which you can download with the URL
http://www.ethereal.com/cgi-bin/viewcvs.cgi/ethereal/tethereal.c.diff?
r2=1.211&r1=1.210&diff_format=u and (re-)build from source. It might
be easier to get the SVN version than to get the patch and apply it to
the 0.10.0a source tarball, but it's probably easier to build from the
source tarball than from the SVN version, as you'll need to have more
tools and make more steps to generate from the SVN version some files
that are bundled with the source tarball.
Note that to build from the 0.10.0a source tarball on Windows with
Microsoft Visual C++, you will need to get a file that was missing
from the 0.10.0a source tarball; see the FAQ for that problem.
Q 5.19: When I run Ethereal on Windows NT, it dies with a Dr. Watson
error, reporting an "Integer division by zero" exception, when I start
it.
A: In at least some case, this appears to be due to using the default
VGA driver; if that's not the correct driver for your video card, try
running the correct driver for your video card.
Q 5.20: When I try to run Ethereal, it complains about
sprint_realloc_objid being undefined.
A: Ethereal can only be linked with version 4.2.2 or later of UCD
SNMP. Your version of Ethereal was dynamically linked with such a
version of UCD SNMP; however, you have an older version of UCD SNMP
installed, which means that when Ethereal is run, it tries to link to
the older version, and fails. You will have to replace that version of
UCD SNMP with version 4.2.2 or a later version.
Q 5.21: I'm running Ethereal on Linux; why do my time stamps have only
100ms resolution, rather than 1us resolution?
A: Ethereal gets time stamps from libpcap/WinPcap, and libpcap/WinPcap
get them from the OS kernel, so Ethereal - and any other program using
libpcap, such as tcpdump - is at the mercy of the time stamping code
in the OS for time stamps.
At least on x86-based machines, Linux can get high-resolution time
stamps on newer processors with the Time Stamp Counter (TSC) register;
for example, Intel x86 processors, starting with the Pentium Pro, and
including all x86 processors since then, have had a TSC, and other
vendors probably added the TSC at some point to their families of x86
processors.
The Linux kernel must be configured with the CONFIG_X86_TSC option
enabled in order to use the TSC. Make sure this option is enabled in
your kernel.
In addition, some Linux distributions may have bugs in their versions
of the kernel that cause packets not to be given high-resolution time
stamps even if the TSC is enabled. See, for example, bug 61111 for Red
Hat Linux 7.2. If your distribution has a bug such as this, you may
have to run a standard kernel from kernel.org in order to get
high-resolution time stamps.
Q 5.22: I'm capturing packets on {Windows 95, Windows 98, Windows Me};
why are the time stamps on packets wrong?
A: This is due to a bug in WinPcap. The bug should be fixed in WinPcap
3.0.
Q 5.23: When I try to run Ethereal on Windows, it fails to run because
it can't find packet.dll.
A: In older versions of Ethereal, there were two binary distributions
available for Windows, one that supported capturing packets, and one
that didn't. The version that supported capturing packets required
that you install the WinPcap driver; if you didn't install it, it
would fail to run because it couldn't find packet.dll.
The current version of Ethereal has only one binary distribution for
Windows; that version will check whether WinPcap is installed and, if
it's not, will disable support for packet capture.
The WinPcap driver and libraries can be downloaded from the WinPcap
Web site, the local mirror of the WinPcap Web site, or the
Wiretapped.net mirror of the WinPcap site.
Q 5.24: I'm running Ethereal on Windows NT/2000/XP/Server; my machine
has a PPP (dial-up POTS, ISDN, etc.) interface, and it shows up in the
"Interface" item in the "Capture Options" dialog box. Why can no
packets be sent on or received from that network while I'm trying to
capture traffic on that interface?
A: WinPcap doesn't support PPP WAN interfaces on Windows
NT/2000/XP/Server; one symptom that may be seen is that attempts to
capture in promiscuous mode on the interface cause the interface to be
incapable of sending or receiving packets. You can disable promiscuous
mode using the -p command-line flag or the item in the "Capture
Preferences" dialog box, but this may mean that outgoing packets, or
incoming packets, won't be seen in the capture.
Q 5.25: I'm running Ethereal on Windows 95/98/Me, on a machine with
more than one network adapter of the same type; Ethereal shows all of
those adapters with the same name, but I can't use any of those
adapters other than the first one.
A: Unfortunately, Windows 95/98/Me gives the same name to multiple
instances of the type of same network adapter. Therefore, WinPcap
cannot distinguish between them, so a WinPcap-based application can
capture only on the first such interface; Ethereal is a
libpcap/WinPcap-based application.
Q 5.26: I'm running Ethereal on Windows, and I'm not seeing any
traffic being sent by the machine running Ethereal.
A: If you are running some form of VPN client software, it might be
causing this problem; people have seen this problem when they have
Check Point's VPN software installed on their machine. If that's the
cause of the problem, you will have to remove the VPN software in
order to have Ethereal (or any other application using WinPcap) see
outgoing packets; unfortunately, neither we nor the WinPcap developers
know any way to make WinPcap and the VPN software work well together.
Also, some drivers for Windows (especially some wireless network
interface drivers) apparently do not, when running in promiscuous
mode, arrange that outgoing packets are delivered to the software that
requested that the interface run promiscuously; try turning
promiscuous mode off.
Q 5.27: I'm trying to capture traffic but I'm not seeing any.
A: Is the machine running Ethereal sending out any traffic on the
network interface on which you're capturing, or receiving any traffic
on that network, or is there any broadcast traffic on the network or
multicast traffic to a multicast group to which the machine running
Ethereal belongs?
If not, this may just be a problem with promiscuous sniffing, either
due to running on a switched network or a dual-speed hub, or due to
problems with the interface not supporting promiscuous mode; see the
response to this earlier question.
Otherwise, on Windows, see the response to this question and, on a
UNIX-flavored OS, see the response to this question.
Q 5.28: I have an XXX network card on my machine; if I try to capture
on it, my machine crashes or resets itself.
A: This is almost certainly a problem with one or more of:
* the operating system you're using;
* the device driver for the interface you're using;
* the libpcap/WinPcap library and, if this is Windows, the WinPcap
device driver;
so:
* if you are using Windows, see the WinPcap support page (or the
local mirror of that page) - check the "Submitting bugs" section;
* if you are using some Linux distribution, some version of BSD, or
some other UNIX-flavored OS, you should report the problem to the
company or organization that produces the OS (in the case of a
Linux distribution, report the problem to whoever produces the
distribution).
Q 5.29: My machine crashes or resets itself when I select "Start" from
the "Capture" menu or select "Preferences" from the "Edit" menu.
A: Both of those operations cause Ethereal to try to build a list of
the interfaces that it can open; it does so by getting a list of
interfaces and trying to open them. There is probably an OS, driver,
or, for Windows, WinPcap bug that causes the system to crash when this
happens; see the previous question.
Q 5.30: Does Ethereal work on Windows Me?
A: Yes, but if you want to capture packets, you will need to install
the latest version of WinPcap, as 2.02 and earlier versions of WinPcap
didn't support Windows Me. You should also install the latest version
of Ethereal as well.
Q 5.31: Does Ethereal work on Windows XP?
A: Yes, but if you want to capture packets, you will need to install
the latest version of WinPcap, as 2.2 and earlier versions of WinPcap
didn't support Windows XP.
Q 5.32: Why doesn't Ethereal correctly identify RTP packets? It shows
them only as UDP.
A: Ethereal can identify a UDP datagram as containing a packet of a
particular protocol running atop UDP only if
1. The protocol in question has a particular standard port number,
and the UDP source or destination port number is that port
2. Packets of that protocol can be identified by looking for a
"signature" of some type in the packet - i.e., some data that, if
Ethereal finds it in some particular part of a packet, means that
the packet is almost certainly a packet of that type.
3. Some other traffic earlier in the capture indicated that, for
example, UDP traffic between two particular addresses and ports
will be RTP traffic.
RTP doesn't have a standard port number, so 1) doesn't work; it
doesn't, as far as I know, have any "signature", so 2) doesn't work.
That leaves 3). If there's RTSP traffic that sets up an RTP session,
then, at least in some cases, the RTSP dissector will set things up so
that subsequent RTP traffic will be identified. Currently, that's the
only place we do that; there may be other places.
However, there will always be places where Ethereal is simply
incapable of deducing that a given UDP flow is RTP; a mechanism would
be needed to allow the user to specify that a given conversation
should be treated as RTP. As of Ethereal 0.8.16, such a mechanism
exists; if you select a UDP or TCP packet, the right mouse button menu
will have a "Decode As..." menu item, which will pop up a dialog box
letting you specify that the source port, the destination port, or
both the source and destination ports of the packet should be
dissected as some particular protocol.
Q 5.33: Why doesn't Ethereal show Yahoo Messenger packets in captures
that contain Yahoo Messenger traffic?
A: Ethereal only recognizes as Yahoo Messenger traffic packets to or
from TCP port 3050 that begin with "YPNS", "YHOO", or "YMSG". TCP
segments that start with the middle of a Yahoo Messenger packet that
takes more than one TCP segment will not be recognized as Yahoo
Messenger packets (even if the TCP segment also contains the beginning
of another Yahoo Messenger packet).
Q 5.34: Why do I get the error
Gdk-ERROR **: Palettized display (256-colour) mode not supported on
Windows.
aborting....
when I try to run Ethereal on Windows?
A: Ethereal is built using the GTK+ toolkit, which supports most
UNIX-flavored OSes, and also supports Windows.
Windows versions of Ethereal before 0.9.14 were built with an older
version of that toolkit, which didn't support 256-color mode on
Windows - it required HiColor (16-bit colors) or more.
Windows versions of Ethereal 0.9.14 and later are built with a version
of that toolkit that supports 256-color mode; upgrade to the current
version of Ethereal if you want to run on a display in 256-color mode.
Q 5.35: When I capture on Windows in promiscuous mode, I can see
packets other than those sent to or from my machine; however, those
packets show up with a "Short Frame" indication, unlike packets to or
from my machine. What should I do to arrange that I see those packets
in their entirety?
A: In at least some cases, this appears to be the result of PGPnet
running on the network interface on which you're capturing; turn it
off on that interface.
Q 5.36: I'm capturing packets on a machine on a VLAN; why don't the
packets I'm capturing have VLAN tags?
A: You might be capturing on what might be called a "VLAN interface" -
the way a particular OS makes VLANs plug into the networking stack
might, for example, be to have a network device object for the
physical interface, which takes VLAN packets, strips off the VLAN
header and constructs an Ethernet header, and passes that packet to an
internal network device object for the VLAN, which then passes the
packets onto various higher-level protocol implementations.
In order to see the raw Ethernet packets, rather than "de-VLANized"
packets, you would have to capture not on the virtual interface for
the VLAN, but on the interface corresponding to the physical network
device, if possible.
Q 5.37: How can I capture raw 802.11 packets, including non-data
(management, beacon) packets?
A: That depends on the operating system on which you're running, and
on the 802.11 interface on which you're capturing.
This would probably require that you capture in promiscuous mode or in
the mode called "monitor mode" or "RFMON mode". On some platforms, or
with some cards, this might require that you capture in monitor mode -
promiscuous mode might not be sufficient. If you want to capture
traffic on networks other than the one with which you're associated,
you will have to capture in monitor mode.
Not all operating systems support capturing non-data packets and, even
on operating systems that do support it, not all drivers, and thus not
all interfaces, support it. Even on those that do, monitor mode might
not be supported by the operating system or by the drivers for all
interfaces.
NOTE: an interface running in monitor mode will, on most if not all
platforms, not be able to act as a regular network interface; putting
it into monitor mode will, in effect, take your machine off of
whatever network it's on as long as the interface is in monitor mode,
allowing it only to passively capture packets.
This means that you should disable name resolution when capturing in
monitor mode; otherwise, when Ethereal (or Tethereal, or tcpdump)
tries to display IP addresses as host names, it will probably block
for a long time trying to resolve the name because it will not be able
to communicate with any DNS or NIS servers.
There are FAQ items below with information on capturing in monitor
mode on Linux, FreeBSD, and NetBSD.
On Windows, you will not be able to capture in monitor mode on any
interfaces, and you might not be able to capture in promiscuous mode,
either. You might have some success in promiscuous mode with Centrino
interfaces, although you will need Ethereal 0.10.6 or later in order
to have the non-data packets recognized and properly dissected.
You will not be able to capture in monitor mode on any other platforms
(including Mac OS X). You might be able to capture in promiscuous
mode, but this won't capture non-data packets.
Q 5.38: How do I capture on an 802.11 device in monitor mode on Linux?
A: Whether you will be able to capture in monitor mode depends on the
card and driver you're using. See this page of Linux 802.11b
information for details on 802.11b wireless cards, including
information on the chips they use, and see this page of Linux
802.11b+/a/g information for details on 802.11b+, 802.11a, and 802.11g
wireless cards, including information on the chips they use.
Cisco Aironet cards:
On Linux with the driver in the 2.4.6 through 2.4.19 kernel:
1. Put the card into monitor mode with the command echo "Mode: rfmon"
>/proc/driver/aironet/interface/Config. If you want to capture
traffic for any BSS rather than just the BSS with which the card
is associated, use "Mode: y" rather than "Mode: rfmon".
2. When the capture completes, turn off monitor mode with the command
echo "Mode: ess" >/proc/driver/aironet/interface/Config.
On Linux with the driver in the 2.4.20 or later kernel, or with the
CVS drivers from the airo-linux SourceForge site, you will have to
capture on the wifiN interface if your Aironet card is ethN, after
running the commands listed above.
In all of those cases, Ethereal would have to be linked with libpcap
0.7.1 or later; this means that most Ethereal binary packages won't
work unless they're statically linked with libpcap 0.7.1 or later, or
they're dynamically linked with libpcap and your system has a libpcap
0.7.1 or later shared library installed (note that libpcap source
package from tcpdump.org does not build shared libraries). Some binary
packaging mechanisms might make it difficult to install Ethereal
binary packages built to depend on older libpcap binary packages if
you have a newer libpcap binary package installed; the installer
programs for those packaging mechanisms might support disabling
dependency checking so that they will install Ethereal even though a
newer version of libpcap is installed.
Cards using the Prism II chip set:
You can capture raw 802.11 packets with Prism II cards on Linux
systems with the 0.1.14-pre6 or later version of the linux-wlan-ng
drivers (see the linux-wlan page, and the linux-wlan-ng tarball
directory), or with the hostap driver for Prism II/2.5/3.
Those require either Solomon Peachy's patch to libpcap 0.7.1 (see his
libpcap-0.7.1-prism.diff file, or his RPMs of that version of
libpcap), or the current CVS version of libpcap, which includes his
patch (download it from the "Current Tar files" section of the
tcpdump.org Web site). If you apply his patches to libpcap 0.7.1 and
rebuild and install libpcap, or if you build and install the current
CVS version of libpcap, you would have to rebuild Ethereal from
source, linking it with that new version of libpcap; an Ethereal
binary package would not work. Ethereal binary packages might work if
you install the libpcap-0.7.1-1prism.i386.rpm RPM, as it might install
a libpcap shared library in place of the one on your system.
With the linux-wlan-ng driver, you should:
1. Put the card into monitor mode with the command wlanctl-ng
interface lnxreq_wlansniffer enable=true. You should request
802.11 headers by adding to that command the option
prismheader=true or, if supported, wlanheader=true; the latter
might require libpcap 0.8.1 or later. You can also set the channel
to monitor by adding the argument channel=channel_number to that
command.
2. When the capture completes, turn off monitor mode with the command
wlanctl-ng interface enable=false. You might also have to turn
802.11 headers off with prismheader=false or wlanheader=false.
See the wlan-ng FAQ for additional information, although note that it
does not appear to be up-to-date.
With the hostap driver, you should:
1. Put the card into monitor mode with the command iwpriv interface
monitor mode, where mode is 2 or 3 (mode 3 would require libpcap
0.8.1 or later).
2. When the capture completes, turn off monitor mode with the command
iwpriv interface monitor 0.
Orinoco Silver and Gold cards:
On Linux systems, the current version of the SourceForge orinoco_cs
driver should support monitor mode. There also exist patches to
earlier versions of the Orinoco driver, on the Orinoco Monitor Mode
Patch Page, to add support for monitor mode. You will have to
determine which version of the driver you have, and select the
appropriate patch, if one is necessary.
Note that the page indicates that not all versions of the Orinoco
firmware support this patch. It says, for some versions of the patch,
"This patch should allow monitor mode with v8.10 firmware (untested w/
8.42);" if you have version 8.10 or later firmware on your Orinoco
cards, you might have to use those patches, with the corresponding
versions of the Orinoco driver, in order to run in monitor mode.
That patch is written for the drivers included with the pcmcia-cs
drivers, but works equally well for the Orinoco drivers provided with
Linux kernels up to 2.4.20. To apply a patch to your kernel drivers,
simply copy the orinoco-09b-patch.diff file to the
/usr/src/linux/drivers/net directory and patch according to the
directions on the Orinoco Monitor Mode Patch Page. You can double-
check the version of the Orinoco drivers that shipped with your kernel
by examining the first few lines of the orinoco.c file.
The Orinoco patches and SourceForge driver require either Solomon
Peachy's patch to libpcap 0.7.1 (see his libpcap-0.7.1-prism.diff
file, or his RPMs of that version of libpcap), or the current CVS
version of libpcap, which includes his patch (download it from the
"Current Tar files" section of the tcpdump.org Web site). If you apply
his patches to libpcap 0.7.1 and rebuild and install libpcap, or if
you build and install the current CVS version of libpcap, you would
have to rebuild Ethereal from source, linking it with that new version
of libpcap; an Ethereal binary package would not work. Ethereal binary
packages might work if you install the libpcap-0.7.1-1prism.i386.rpm
RPM, as it might install a libpcap shared library in place of the one
on your system.
With a driver that supports monitor mode, you should:
1. Put the card into monitor mode with the command iwpriv interface
monitor mode channel_number, where mode is 1 or 2, and
channel_number is the number of the channel to monitor.
2. When the capture completes, turn off monitor mode with the command
iwpriv interface monitor 0.
Cards with the Texas Instruments ACX100 chipset:
You can capture raw 802.11 packets with ACX100 cards on Linux systems
with the ACX100 OSS drivers available from the ACX100 wireless network
driver project SourceForge site.
With that driver:
1. Put the card into monitor mode with the command iwpriv interface
monitor 2 channel_number, where channel_number is the number of
the channel to monitor.
2. When the capture completes, turn off monitor mode with the command
iwpriv interface monitor 0.
Cards with Atheros Communications chipsets:
You can capture raw 802.11 packets with AR5K cards on Linux systems
with the v5_ar5k or madwifi drivers. For the v5ar5k driver you will
need the Linux wireless-tools version 25 or higher to put the card
into monitor mode. If you're using the madwifi driver, you can put the
card into monitor mode using iwconfig interface mode monitor, followed
by iwconfig interface channel channel to select a channel (if needed).
Other cards:
It might be possible to capture in monitor mode on other cards. If so,
please supply us with information on how to do so, so that we can
incorporate that information into this FAQ in the future.
Q 5.39: How do I capture on an 802.11 device in monitor mode on
FreeBSD?
A: On FreeBSD 5.2 and later, you should be able to capture in monitor
mode on 802.11 interfaces supported by the wi and acx drivers, if
Ethereal is linked with libpcap 0.8.1 or later, and on 802.11
interfaces supported by the an driver, if Ethereal is linked with
libpcap 0.7.1 or later.
For cards supported by the wi and acx drivers, you should:
1. Put the card into monitor mode with the command ifconfig interface
monitor. You can also set the channel to monitor by adding the
argument channel channel_number to that command.
2. When you start the capture, in Ethereal select "802.11" as the
"Link-layer header type", and in Tethereal add the command-line
argument -y 802.11.
3. When the capture completes, turn off monitor mode with the command
ifconfig interface -monitor.
For cards supported by the an driver, you should:
1. Put the card into monitor mode with the command ancontrol -i
interface -M flag, where flag should be the sum of:
+ 1, to turn monitor mode on;
+ 2, if you want to capture traffic from any BSS rather than
just the BSS with which the card is associated;
+ 4, if you want to see beacon packets (capturing beacon
packets increases the CPU requirements of capturing).
2. When the capture completes, turn off monitor mode with the command
ancontrol -i interface -M 0.
Don't add 8 in to flag; Ethereal currently doesn't support the full
Aironet header.
On FreeBSD 4.6 through 5.1, you should be able to capture in monitor
mode on 802.11 interfaces supported by the an driver, but not on any
other interfaces; see the instructions for FreeBSD 5.2 or later for
those cards.
In FreeBSD 4.5 and earlier, you will not be able to capture in monitor
mode on 802.11 interfaces (no drivers supported it prior to 4.5, and
in 4.5 the an driver had bugs that caused packets not to be captured
correctly).
Q 5.40: How do I capture on an 802.11 device in monitor mode on
NetBSD?
A: On NetBSD 2.0-beta and later, you should be able to capture in
monitor mode on 802.11 interfaces supported by the wi and acx drivers,
if Ethereal is linked with libpcap 0.8.1 or later. The instructions
are the same as for FreeBSD 5.2 and later.
Q 5.41: I'm trying to capture 802.11 traffic on Windows; why am I not
seeing any packets?
A: At least some 802.11 card drivers on Windows appear not to see any
packets if they're running in promiscuous mode. Try turning
promiscuous mode off; you'll only be able to see packets sent by and
received by your machine, not third-party traffic, and it'll look like
Ethernet traffic and won't include any management or control frames,
but that's a limitation of the card drivers.
Q 5.42: I'm trying to capture 802.11 traffic on Windows; why am I
seeing packets received by the machine on which I'm capturing traffic,
but not packets sent by that machine?
A: This appears to be another problem with promiscuous mode; try
turning it off.
Q 5.43: How can I capture packets with CRC errors?
A: Ethereal can capture only the packets that the packet capture
library - libpcap on UNIX-flavored OSes, and the WinPcap port to
Windows of libpcap on Windows - can capture, and libpcap/WinPcap can
capture only the packets that the OS's raw packet capture mechanism
(or the WinPcap driver, and the underlying OS networking code and
network interface drivers, on Windows) will allow it to capture.
Unless the OS always supplies packets with errors such as invalid CRCs
to the raw packet capture mechanism, or can be configured to do so,
invalid CRCs to the raw packet capture mechanism, Ethereal - and other
programs that capture raw packets, such as tcpdump - cannot capture
those packets. You will have to determine whether your OS needs to be
so configured and, if so, can be so configured, configure it if
necessary and possible, and make whatever changes to libpcap and the
packet capture program you're using are necessary, if any, to support
capturing those packets.
Most OSes probably do not support capturing packets with invalid CRCs
on Ethernet, and probably do not support it on most other link-layer
types. Some drivers on some OSes do support it, such as some Ethernet
drivers on FreeBSD; in those OSes, you might always get those packets,
or you might only get them if you capture in promiscuous mode (you'd
have to determine which is the case).
Note that libpcap does not currently supply to programs that use it an
indication of whether the packet's CRC was invalid (because the
drivers themselves do not supply that information to the raw packet
capture mechanism); therefore, Ethereal will not indicate which
packets had CRC errors unless the FCS was captured (see the next
question) and you're using Ethereal 0.9.15 and later, in which case
Ethereal will check the CRC and indicate whether it's correct or not.
Q 5.44: How can I capture entire frames, including the FCS?
A: Ethereal can only capture data that the packet capture library -
libpcap on UNIX-flavored OSes, and the WinPcap port to Windows of
libpcap on Windows - can capture, and libpcap/WinPcap can capture only
the data that the OS's raw packet capture mechanism (or the WinPcap
driver, and the underlying OS networking code and network interface
drivers, on Windows) will allow it to capture.
For any particular link-layer network type, unless the OS supplies the
FCS of a frame as part of the frame, or can be configured to do so,
Ethereal - and other programs that capture raw packets, such as
tcpdump - cannot capture the FCS of a frame. You will have to
determine whether your OS needs to be so configured and, if so, can be
so configured, configure it if necessary and possible, and make
whatever changes to libpcap and the packet capture program you're
using are necessary, if any, to support capturing the FCS of a frame.
Most OSes do not support capturing the FCS of a frame on Ethernet, and
probably do not support it on most other link-layer types. Some
drivres on some OSes do support it, such as some (all?) Ethernet
drivers on NetBSD and possibly the driver for Apple's gigabit Ethernet
interface in Mac OS X; in those OSes, you might always get the FCS, or
you might only get the FCS if you capture in promiscuous mode (you'd
have to determine which is the case).
Versions of Ethereal prior to 0.9.15 will not treat an Ethernet FCS in
a captured packet as an FCS. 0.9.15 and later will attempt to
determine whether there's an FCS at the end of the frame and, if it
thinks there is, will display it as such, and will check whether it's
the correct CRC-32 value or not.
Q 5.45: Why does Ethereal hang after I stop a capture?
A: The most likely reason for this is that Ethereal is trying to look
up an IP address in the capture to convert it to a name (so that, for
example, it can display the name in the source address or destination
address columns), and that lookup process is taking a very long time.
Ethereal calls a routine in the OS of the machine on which it's
running to convert of IP addresses to the corresponding names. That
routine probably does one or more of:
* a search of a system file listing IP addresses and names;
* a lookup using DNS;
* on UNIX systems, a lookup using NIS;
* on Windows systems, a NetBIOS-over-TCP query.
If a DNS server that's used in an address lookup is not responding,
the lookup will fail, but will only fail after a timeout while the
system routine waits for a reply.
In addition, on Windows systems, if the DNS lookup of the address
fails, either because the server isn't responding or because there are
no records in the DNS that could be used to map the address to a name,
a NetBIOS-over-TCP query will be made. That query involves sending a
message to the NetBIOS-over-TCP name service on that machine, asking
for the name and other information about the machine. If the machine
isn't running software that responds to those queries - for example,
many non-Windows machines wouldn't be running that software - the
lookup will only fail after a timeout. Those timeouts can cause the
lookup to take a long time.
If you disable network address-to-name translation - for example, by
turning off the "Enable network name resolution" option in the
"Capture Options" dialog box for starting a network capture - the
lookups of the address won't be done, which may speed up the process
of reading the capture file after the capture is stopped. You can make
that setting the default by selecting "Preferences" from the "Edit"
menu, turning off the "Enable network name resolution" option in the
"Name resolution" options in the preferences disalog box, and using
the "Save" button in that dialog box; note that this will save all
your current preference settings.
If Ethereal hangs when reading a capture even with network name
resolution turned off, there might, for example, be a bug in one of
Ethereal's dissectors for a protocol causing it to loop infinitely. If
you're not running the most recent release of Ethereal, you should
first upgrade to that release, as, if there's a bug of that sort, it
might've been fixed in a release after the one you're running. If the
hang occurs in the most recent release of Ethereal, the bug should be
reported to the Ethereal developers' mailing list at
ethereal-dev@ethereal.com.
On UNIX-flavored OSes, please try to force Ethereal to dump core, by
sending it a SIGABRT signal (usually signal 6) with the kill command,
and then get a stack trace if you have a debugger installed. A stack
trace can be obtained by using your debugger (gdb in this example),
the Ethereal binary, and the resulting core file. Here's an example of
how to use the gdb command backtrace to do so.
$ gdb ethereal core
(gdb) backtrace
..... prints the stack trace
(gdb) quit
$
The core dump file may be named "ethereal.core" rather than "core" on
some platforms (e.g., BSD systems).
Also, if at all possible, please send a copy of the capture file that
caused the problem; when capturing packets, Ethereal normally writes
captured packets to a temporary file, which will probably be in /tmp
or /var/tmp on UNIX-flavored OSes, \TEMP on the main system disk
(normally C:) on Windows 9x/Me/NT 4.0, and \Documents and
Settings\your login name\Local Settings\Temp on the main system disk
on Windows 2000/XP/Server 2003, so the capture file will probably be
there. It will have a name beginning with ether, with some mixture of
letters and numbers after that. Please don't send a trace file greater
than 1 MB when compressed; instead, make it available via FTP or HTTP,
or say it's available but leave it up to a developer to ask for it. If
the trace file contains sensitive information (e.g., passwords), then
please do not send it.
Q 5.46: How can I search for, or filter, packets that have a
particular string anywhere in them?
A: If you want to do this when capturing, you can't. That's a feature
that would be hard to implement in capture filters without changes to
the capture filter code, which, on many platforms, is in the OS kernel
and, on other platforms, is in the libpcap library.
In releases prior to 0.9.14, you also can't search for, or filter,
packets containing a particular string even after you've captured
them.
In 0.9.14, you can search for, but not filter, packets that have a
particular string; this has been added to the "Find Frame" dialog
("Find Frame" under the "Edit" menu, or control-F).
In 0.9.15 and later, you can search for those packets using either the
mechanism introduced in 0.9.14 or using the new "contains" operator in
filter expressions, which lets you search the entire packet or text
string or byte string fields in the packet; the "contains" operator
can also be used in expressions used to filter the display.
Q 5.47: How do I filter a capture to see traffic for virus XXX?
A: For some viruses/worms there might be a capture filter to recognize
the virus traffic. Check the CaptureFilters page on the Ethereal Wiki
to see if anybody's added such a filter.
Note that Ethereal was not designed to be an intrusion detection
system; you might be able to use it as an IDS, but in most cases
software designed to be an IDS, such as Snort or Prelude, will
probably work better.
The Bleeding Edge of Snort has a collection of signatures for Snort to
detect various viruses, worms, and the like.
Please send support questions about Ethereal to the
ethereal-users[AT]ethereal.com mailing list.
For corrections/additions/suggestions for this web page (and not
Ethereal support questions), please send email to
ethereal-web[AT]ethereal.com .
Last modified: Thu, November 18 2004.
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