Re: ICMP Redirect interpretation

From: Barry Margolin (barmar@genuity.net)
Date: 03/25/02 

From: Barry Margolin <barmar@genuity.net>
Date: Mon, 25 Mar 2002 19:21:23 GMT

In article <4b82e88a.0203250132.6ccf058f@posting.google.com>,
bsduser <daryn_lightblade@yahoo.com> wrote:
>I'm not sure how to interpret this .. what are all those "redirect
>host" packets ? does this mean that a.b.c.d is sending the server ICMP
>Redirect packets asking the server to re-route to w.x.y.z ? if so, why

Yes.

>would it be sending them to this host ? a.b.c.d is two hops away, as
>can be seen from the traceroute below :
>
> 1 e.f.g.h (e.f.g.h) 19.689 ms 19.890 ms 19.965 ms
> 2 a.b.c.d (a.b.c.d) 29.956 ms 29.929 ms 29.967 ms
> 3 w.x.y.z (w.x.y.z) 30.019 ms 29.944 ms 29.967 ms

Whenever a router sends a redirect, it *also* forwards the packet to the
alternate router. Since you're ignoring the redirects, a.b.c.d is
effectively two hops away, because it doesn't get the packets until e.f.g.h
forwards to it. 

-- 
Barry Margolin, barmar@genuity.net
Genuity, Woburn, MA
*** DON'T SEND TECHNICAL QUESTIONS DIRECTLY TO ME, post them to newsgroups.
Please DON'T copy followups to me -- I'll assume it wasn't posted to the group.

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