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Re: simple question as always..
From: Danny McPherson <[email protected]> Subject: Re: simple question as always.. Date: Mon, 09 Mar 1998 18:33:56 -0700 Message-ID: <[email protected]> Hi, tatsuya> could someone explain to me why I can ping but traceroute tatsuya> seems to have problem reaching it. > The combination of a firewall (permitting ICMP echo replies/requests, but > filtering your UDP traceroute probes) .. and a traceroute client that > doesn't correctly handle (IMO) the response (ICMP Type 3, Code 13: > Communication Administratively Prohibited). tracert with WindowsNT4.0 uses ICMP ECHO messages for probing packets. Hence one might go through the filtering router boxes. :) tatsuya> I was told once that traceroute required each router on the tatsuya> way to KNOW something whereas ping does not. tatsuya> I just can not recall what this something is and I am tatsuya> intend to find out. traceroute ends its probing when it receives a ICMP port unreachable message. Filtered by an IP gateway like cisco boxes, it receives Communication Administratively Prohibited messages and continues probing by incrementing IP TTL. ------- Toshio Shigematsu