Ping & traceroute

[suthomas1]

In firewalls or in routers, if we ping is blocked using icmp..which disallows ping responses.

But doesnt traceroute use icmp as well,so shouldnt blocking icmp disallow traceroute also or is it blocked by using ports above 64000 range?

In a case, trace to a particular ip drops after certain hops (due to firewalls in those hops), but if we ping to that ip , response is received.How is that possible?

Thanks.

[Thotsaphon Lueangwattanaphong]

Sunny,

Ping and Traceroute are not State-full. Well, You may inspect Ping. But traceroute is another story. Windows uses ICMP echoes by default. Linux OS's use UDP by default. Cisco IOS use UDP.

So you may receive the traceroute packets replied by the devices as ttl-exceed ,port-unreachable or echo-reply.

That's why you always get "*" when doing tracceroute via firewall. You have to allow things.

HTH,

Toshi