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Specify Outgoing/Responding IP

Have Cisco 37xx series router. On its DS3 wan interface it has a 99.x.x.x public IP address. On its lan interface it has a 172.x.x.x private IP address. The 172 address just routes between it and another linux based router. When doing traceroutes through the router when the source is on the lan side it responds using the 172 IP. I would like it to respond to all requests using the 99.x.x.x IP. How do I do that?

I accomplish this on the linux based router with preferred source but not sure on cisco.

M
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M
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M, That's an interesting question. - Routers (in general) should decrement the TTL on the incoming interface - which is how the router knows to send the TTL expired ICMP packet. And Cisco routers normally source a packet based on the exiting interface's IP. Cisco has several "ip source" commands to change that behavior.

Here are the one's I could find: cdp source-interface ip admission source-interface ip domain-lookup source-interface ip flow-export source ip ftp source-interface ip kerberos source-interface ip radius source-interface ip rcmd source-interface ip ssh source-interface ip tacacs source-interface ip telnet source-interface ip tftp source-interface ip udptn source-interface logging source-interface ntp source sgbp source-ip snmp-server trap-source

As you can see they are protocol specific and none of them are for ICMP or TTL-Expired.

JC

Reply to
J.Cottingim

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