Jumbo frames coming from Catalyst 3100

[Colin Higgins]

I have a Cisco Catalyst 3100 blade in a Dell server chassis that is trunked to a 6509.

When doing a protocol capture, I see large frames being sent from one of the servers in the chassis.

Example:

TCP:[Continuation to #1701] [Bad CheckSum]Flags=...AP...,   SrcPort=HTTP(80), DstPort=2667, PayloadLen=2831, Seq=1489611217 - 1489614048,   Ack=1719592331, Win=65535

I see lengths up to 6900+ bites coming from the server.

The switch has the global MTU set to 1500

system mtu routing 1500

and I can't seem to set this at the interface level.

The server is configured to send 1500 length frames.

Why am I seeing these jumbos? (the server is Windows 2003)

[Reza Sharifi]

6900+ bites

Are these in bits or bytes?

The 3100 series switches are very similar to 3560 and 3750 series switches and on all these switches Jumbo frame can only be enabled globally.

HTH

[Colin Higgins]

I discovered much to my annoyance that the giants reported in WireShark were a result of the "

Generic Segmentation Offload feature" on my Linux distribution (Back Track Ubuntu)

http://www.unleashnetworks.com/blog/?p=307

Not even sure how to turn this feature off