17 lines
1.0 KiB
Plaintext
17 lines
1.0 KiB
Plaintext
The roadwarriors <b>alice</b> and <b>venus</b> sitting behind the router <b>moon</b> set up
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tunnels to gateway <b>sun</b>. Since both roadwarriors possess the same 10.1.0.0/25 subnet,
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gateway <b>sun</b> uses Source NAT after ESP decryption to map these subnets to PH_IP_CAROL10
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and PH_IP_DAVE10, respectively.
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<p/>
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In order to differentiate between the tunnels to <b>alice</b> and <b>venus</b>, respectively,
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<b>XFRM marks</b> are defined for both the inbound and outbound IPsec SAs and policies using
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the <b>mark_in</b> and <b>mark_out</b> parameters in ipsec.conf.
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<p/>
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<b>iptables -t mangle</b> rules are then used in the PREROUTING chain to mark the traffic to
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and from <b>alice</b> and <b>venus</b>, respectively.
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<p/>
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The script designated by <b>leftupdown=/etc/mark_updown</b> automatically inserts
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iptables mangle rules that mark the inbound ESP packets as well as iptables IPsec-policy rules
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that let pass the tunneled traffic. In order to test the tunnel, the hosts <b>alice</b>
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and <b>venus</b> ping the client <b>bob</b> behind the gateway <b>sun</b>.
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