[BBLISA] Connecting 10GBE to GigE

[Daniel Feenberg]

We have a Brocade 24 port 10GBE switch connected to a Dell GigE switch 
using one of the 4 GigE ports on the Brocade. There is NFS traffic accross 
the link, not much else. Every few weeks the link refuses to carry any 
traffic. Details:

   0) There is no error message on the Brocade console.
   1) The lights on both switches say the link is up.
   2) Power-cycling the Dell has no effect.
   3) There are devices on the other 3 GigE ports, they are
      unaffected.
   4) Replacing the Dell with Netgear has no effect.
   5) The Brocade says the link is up, but if the link is disabled
      the Brocade won't reenable it.
   6) Traffic within each switch is normal - only the link is affected.
   7) A warm boot of the Brocade restores service every time.

Any thoughts about what could cause this? I don't think it is a problem 
with the patch cable (0% packet loss) or a loop (checked for that), or 
authentication (switch is in factory default configuration other than IP 
address and logging).

Is there some reason that NFS can't negotiate the difference in speed?

dan feenberg