Re: 2.4.20 Broken Path MTU Discovery?

From: Andi Kleen (ak@suse.de)
Date: Sun Feb 02 2003 - 19:29:51 EST


"Carlos Velasco" <carlosev@newipnet.com> writes:
>
> ¿May be the Linux box is giving up PMTU? ¿Why? it now knows MTU is 400.
> I have others windows boxes in the network, they work fine with PMTU.

A MTU of 400 is illegal, IPv4 requires a minimum MTU of 576 bytes. Below
it linux uses the minimum MTU and turns off path mtu discovery (=
drops DF)

You can change that minimum mtu by changing the ip_rt_min_pmtu variable
(no sysctl, you have to change it in /dev/kmem or recompile)

-Andi
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