diff --git a/ipppd/configure.in b/ipppd/configure.ac
similarity index 65%
rename from ipppd/configure.in
rename to ipppd/configure.ac
index 952afe6c..55a3d009 100644
--- a/ipppd/configure.in
+++ b/ipppd/configure.ac
@@ -1,37 +1,49 @@
 dnl Process this file with autoconf to produce a configure script.
+
+AC_PREREQ([2.68])
+
 AC_INIT(auth.c)
-AC_CONFIG_HEADER(config.h)
+dnl AC_PREFIX_DEFAULT([/usr])
 
 I4LVERSION=${I4LVERSION:-"?.?"}
 MANDATE=`grep CHECKIN ipppd.man.in | awk '{print $4}'`
-CONFIG_MANDIR=`eval echo ${CONFIG_MANDIR:-"/usr/man"}`
-CONFIG_SBINDIR=`eval echo ${CONFIG_SBINDIR:-"/sbin"}`
-CONFIG_RUNDIR=`eval echo ${CONFIG_RUNDIR:-"/var/run"}`
+CONFIG_MANDIR=${mandir:-"/usr/man"}
+CONFIG_SBINDIR=${sbindir:-"/sbin"}
+CONFIG_RUNDIR=${CONFIG_RUNDIR:-"/var/run"}
 CONFIG_IPPPD_MSCHAP=${CONFIG_IPPPD_MSCHAP:-"n"}
 CONFIG_IPPPD_RADIUS=${CONFIG_IPPPD_RADIUS:-"n"}
 CONFIG_IPPP_FILTER=${CONFIG_IPPP_FILTER:-"n"}
 CONFIG_RADIUS_WTMP_LOGGING=${CONFIG_RADIUS_WTMP_LOGGING:-"n"}
-RADIUS_CLIENT_CONFIG_FILE=`eval echo ${RADIUS_CLIENT_CONFIG_FILE:-"/usr/local/lib/radiusclient/radiusclient.conf"}`
+RADIUS_CLIENT_CONFIG_FILE=${RADIUS_CLIENT_CONFIG_FILE:-"/usr/local/lib/radiusclient/radiusclient.conf"}
+
 dnl Checks for programs.
 AC_PROG_INSTALL
 AC_PROG_CC
 
 dnl Checks for libraries.
-AC_CHECK_LIB(bsd, daemon,HAVE_LIBBSD=1; AC_DEFINE(HAVE_LIBBSD, [], [libbsd available]),
+AC_CHECK_LIB(bsd, daemon,
+	HAVE_LIBBSD=1; AC_DEFINE(HAVE_LIBBSD, [], [libbsd available]),
 	[AC_MSG_WARN(Could not find libbsd, build disabled)])
 dnl Replace `main' with a function in -lcrypt:
-AC_CHECK_LIB(crypt, main,HAVE_LIBCRYPT=1; AC_DEFINE(HAVE_LIBCRYPT, [], [libcrypt available]))
-AC_CHECK_LIB(des, des_ecb_encrypt, HAVE_LIBDES=1; AC_DEFINE(HAVE_LIBDES, [], [libdes available]))
-AC_CHECK_LIB(ssl, DES_ecb_encrypt, HAVE_LIBSSL=1; AC_DEFINE(HAVE_LIBSSL, [], [libssl available]))
+AC_CHECK_LIB(crypt, main,
+	[HAVE_LIBCRYPT=1; AC_DEFINE(HAVE_LIBCRYPT, [], [libcrypt available])])
+AC_CHECK_LIB(des, des_ecb_encrypt,
+	[HAVE_LIBDES=1; AC_DEFINE(HAVE_LIBDES, [], [libdes available])])
+AC_CHECK_LIB(ssl, DES_ecb_encrypt,
+	[HAVE_LIBSSL=1; AC_DEFINE(HAVE_LIBSSL, [], [libssl available])])
 
 dnl Checks for header files.
 AC_HEADER_STDC
 AC_HEADER_SYS_WAIT
 AC_CHECK_HEADERS(fcntl.h limits.h paths.h sys/file.h sys/ioctl.h sys/time.h syslog.h unistd.h)
-AC_CHECK_HEADER(shadow.h, HAVE_SHADOW_H=1; AC_DEFINE(HAVE_SHADOW_H, [], [shadow.h available]))
-AC_CHECK_HEADER(linux/isdn_lzscomp.h, HAVE_LZSCOMP_H=1; AC_DEFINE(HAVE_LZSCOMP_H, [], [isdn_lzscomp.h available]))
-AC_CHECK_HEADER(pcap-bpf.h, [HAVE_PCAP_BPF_H=1; AC_DEFINE(HAVE_PCAP_BPF_H, [], [pcap-bpf.h availabe])],
-	[AC_CHECK_HEADER(net/bpf.h, [HAVE_NET_BPF_H=1; AC_DEFINE(HAVE_NET_BPF_H, [], [net/bpf.h available])],
+AC_CHECK_HEADER(shadow.h,
+	[HAVE_SHADOW_H=1; AC_DEFINE(HAVE_SHADOW_H, [], [shadow.h available])])
+AC_CHECK_HEADER(linux/isdn_lzscomp.h,
+	[HAVE_LZSCOMP_H=1; AC_DEFINE(HAVE_LZSCOMP_H, [], [isdn_lzscomp.h available])])
+AC_CHECK_HEADER(pcap-bpf.h,
+	[HAVE_PCAP_BPF_H=1; AC_DEFINE(HAVE_PCAP_BPF_H, [], [pcap-bpf.h availabe])],
+	[AC_CHECK_HEADER(net/bpf.h,
+		[HAVE_NET_BPF_H=1; AC_DEFINE(HAVE_NET_BPF_H, [], [net/bpf.h available])],
 		[AC_MSG_ERROR(Could not find pcap header file)])])
 
 dnl Checks for typedefs, structures, and compiler characteristics.
@@ -42,28 +54,13 @@ AC_TYPE_UID_T
 
 dnl Checks for library functions.
 AC_TYPE_GETGROUPS
-AC_PROG_GCC_TRADITIONAL
 AC_FUNC_MEMCMP
 AC_FUNC_VPRINTF
 AC_CHECK_FUNCS(gethostname gettimeofday select socket strdup strerror strtol strtoul uname)
 
-dnl Optional sbin directory
-AC_ARG_WITH(sbin,
-	[  --with-sbin=DIR         Set directory where ipppd is istalled. [/sbin]],
-	CONFIG_SBINDIR="${withval}"
-	AC_DEFINE(CONFIG_SBINDIR,"${withval}", [sbin directory]),
-)
-
-dnl Optional man directory
-AC_ARG_WITH(sbin,
-	[  --with-man=DIR          Set manpage directory. [/usr/man]],
-	CONFIG_MANDIR="${withval}"
-	AC_DEFINE(CONFIG_MANDIR,"${withval}", [manual directory]),
-)
-
 dnl Optional /var/run directory
-AC_ARG_WITH(sbin,
-	[  --with-varrun=DIR       Set directory for .pid files. [/var/run]],
+AC_ARG_WITH(rundir,
+	[  --with-rundir=DIR       Set directory for .pid files. [/var/run]],
 	CONFIG_RUNDIR="${withval}"
 	AC_DEFINE(CONFIG_RUNDIR,"${withval}", [directory for run files]),
 )
@@ -109,6 +106,7 @@ AC_ARG_ENABLE(ippp-filter,
 	AC_DEFINE(CONFIG_IPPP_FILTER,"y", [IPPP filters enabled]),
 )
 
+dnl Define which variables to substitute & which files to generate
 AC_SUBST(I4LVERSION)
 AC_SUBST(MANDATE)
 AC_SUBST(HAVE_LIBDES)
@@ -128,4 +126,6 @@ AC_SUBST(RADIUS_CLIENT_CONFIG_FILE)
 AC_SUBST(CONFIG_RADIUS_WTMP_LOGGING)
 AC_SUBST(CONFIG_IPPPD_DEBUGFLAGS)
 AC_SUBST(CONFIG_IPPP_FILTER)
+AC_CONFIG_HEADERS(config.h)
+
 AC_OUTPUT(Makefile ipppd.man pathnames.h)