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Jumbo Frame issues.

Trusted Contributor

Jumbo Frame issues.

Eli was looking to help a customer with Ethernet jumbo frame issues:




1.  The servers are on the HP chassis on the same vlan, same subnet 

2.  we have tried sniff the traffic using port mirroring on both ports  of server A and B in the HP switch but couldn't find anything good


      1.  The switch jumbo settings is turned off 

       2.  we have done  offloads to the interface as well in server B..

> [root@SPCACT-MSP02 network-scripts]# ethtool -k eth2 Offload

> parameters for eth2:

> Cannot get device udp large send offload settings: Operation not  supported

> rx-checksumming: off

> tx-checksumming: off

> scatter-gather: off

> tcp segmentation offload: off

> udp fragmentation offload: off

> generic segmentation offload: off



 Can you please advise how to disable the Jumbo frame.




Rick had some advice:




Then I suspect what you and your customer are seeing is the result of LRO/GRO - large receive offload - where the NIC or low down in the stack (before the packet sniffing point) will coalesce consecutive segments of a TCP connection together.  It is rather like the receive side version of TSO (TCP Segmentation Offload).


So, you might look into using ethtool to disable LRO on the interface in question.  Assuming the ethtool knows about it in the bits you are running.  Otherwise, you may need to go hunting for module parms.




Any other advice or comments for Eli?