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Subject: Re: path MTU discovery issue
From: Tim Harrison (harrisontimharrison.com)
Date: Wed Sep 06 2000 - 10:50:39 CDT

Rask Ingemann Lambertsen wrote:

> I think that if you have path MTU discovery compiled into the kernel,
> then you can use /proc to control it:
>
> $ cat /proc/sys/net/ipv4/ip_no_pmtu_disc
> 0

My ip_no_pmtu_disc == 0. If I change it to 1, I still get the same
problem.

> The documentation is your friend.

It is, indeed. I read it. Unfortunately, I still have the problem.

After doing repeated pings backwards, starting at the remote mail
server, I found that for both networks that I'm trying to reach, there's
a hop along the way that doesn't respond if you use: ping -D -s 1472
x.x.x.x. So, I assume that there's a router along the way that's
causing the problems. But, considering I've turned on and off path MTU
discovery, it should have worked sometime.

Tim Harrison
Network Engineer
Bird On A Wire Networks
http://www.boaw.net/