[OpenAFS] Re: mtu problem

Andrew Deason adeason@sinenomine.net
Thu, 7 Feb 2013 09:16:59 -0600

On Thu, 7 Feb 2013 11:09:28 +0000 (GMT)
Antony Mayi <antonymayi@yahoo.com> wrote:

> I seem to have problem with one particular client that is unable to
> access AFS. When tcpdumping both sides I can see the server sends some
> packets that are 1488B long and non of these ever arrives to the
> client so this points out to a MTU problem (verified with ping).

If the MTU is lower, the packets should still get there; they should
just be fragmented and then reassembled. But you may have something that
drops UDP fragments, which is pretty common (or something that's just
dropping UDP packets over a certain size for some reason).

> Is there a way to work this around on the client's side? This is just
> a single client suffering so don't want to decrease the MTU on all the
> servers just because of one client. And decreasing it just on the
> client side doesn't make any difference.

By "decreasing it on the client side", so you mean you adjusted the
actual interface MTU? You can try forcing the max packet size Rx uses
with the -rxmaxmtu option to afsd. Say, 'afsd -rxmaxmtu 1200'.

Andrew Deason