Greetings,

Am running a Cisco PIX 525 with OS v7.2. I am trying to enable traceroute through PIX. I already have the below config on my firewall for allowing ICMP replies from untrusted i/f.

access-list xxxx extended permit icmp any any echo-reply

access-list xxxx extended permit icmp any any unreachable

access-list xxxx extended permit icmp any any time-exceeded

I want to allow these replies from anyone on the untrusted i/f, meaning I don't want to control my users to traceroute only some destinations. At the same time, I am worried that anyone can send a crafted echo-reply flood packet(s) to my network.

Is there any other secured way of allowing ICMP replies into my network? (No suggestions of H/W upgrade please. Planning to replace this PIX with a netscreen if this is the only way PIX can work.)

Suggestions are appreciated.

Thanks,

Krishna, CISSP, CCSP