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Scott Forsyth
Asked: 2010-01-26 20:07:05 +0800 CST

Why isn't ICMP routing with iptables nat routing

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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?

router nat iptables icmp

1 Answers

  1. Best Answer

    Have you done any pcapping to see if the icmp packets are getting NAT'd and sent out again? Maybe they're just being accepted by the box you're running iptables on.

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