Jumbo frames from 1750 to NetApp filer

David Bloomfield dxb-linuxpe at tesla.ioppublishing.com
Tue May 18 09:21:01 CDT 2004

Hi all,

I'm trying to get jumbo frames working between a PE1750 running RHEL ES
3 (patched up to date) and a NetApp FAS940 filer.

The server has an Intel PRO/1000 MT dual port card as well as the two
embedded Broadcom ports. 

Both server and filer are connected to an Extreme Summit 7i switch,
connecting at 1000 Mb/s, full duplex.

With everything configured for an MTU of 9000, NFS access from the
server to the filer completely hangs as soon as more than a trivial
amount of traffic is transferred. Once this happens, all further NFS
requests block, even using things like "df".

If the MTU somewhere along the chain is dropped back to 1500, NFS access
returns, including anything left hanging from before.

I'm aware of a possible issue with the Intel card and MTU values greater
than 8998, but I've tried using a lower value, and anyway, this problem
also occurs when using the Broadcom ports. 

The driver modules (e1000 and tg3) are those supplied in the kernel
(currently 2.4.21-15.ELsmp), and the NFS mount options are:


Any thoughts welcome.


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