[OpenAFS] OpenAFS, Cisco VPN and MAC OS and mtu

Douglas E. Engert deengert@anl.gov
Fri, 15 May 2009 15:37:34 -0500

We are having problems with Mac OS 10.4 and 10.5  using Cisco VPN
AFS can become unusable.  Mac 10.4 is running OpenAFS 1.4.8 for sure.
I think the Mac 10.5 is running OpenAFS 1.5.59.

Using rxdebug and looking at the natMTU parameter, on most Unix systems
this is 1444,(1500 - 56) as expected. On Windows systems this is usually
1260.  And on MAC it is 1444.

Even if I set the interface mtu 1244, and reboot the MAC, rxdebug shows
the interface is using 1244 but rxdebug continues to show a natMTU = 1444.
as though it still assumed the mtu was 1500.

So it looks like the MAC client is not getting the existingMTU
from the OS in util/netutils.c

The AFS client on Windows has the RxMaxMTU (1244 appears to be the best
setting). Is there any equivelent option for the MAC?

Any thoughts on this?


  Douglas E. Engert  <DEEngert@anl.gov>
  Argonne National Laboratory
  9700 South Cass Avenue
  Argonne, Illinois  60439
  (630) 252-5444