Why isn't ICMP routing with iptables nat routing

Posted by Scott Forsyth - MVP on Server Fault See other posts from Server Fault or by Scott Forsyth - MVP
Published on 2010-01-26T04:07:05Z Indexed on 2010/03/08 4:38 UTC
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I'm using iptables on Ubuntu server to route a public IP to a private IP. I want to nat all traffic, including 80, 443 and ICMP.

However, it appears that ICMP isn't routing. I have a steady ping going to the public IP and it never stops, even with NAT pointing to a bogus IP.

Here are the rules that I'm using:

iptables -t nat -I PREROUTING -d 206.72.119.76 -j DNAT --to-destination 10.240.5.5  
iptables -t nat -I POSTROUTING  -s 10.240.5.5 -j SNAT --to-source 206.72.119.76

I tried with rules for ICMP specifically, but no such luck:

iptables -t nat -I PREROUTING -d 206.72.119.76 - icmp --icmp-type echo-request -j DNAT --to-destination 10.240.5.5

Any ideas?

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