Q&A - VSS and Jumbo Frames

April 28, 2009 by ted.

Ted,

I currently have a new blade chassis connected to my Nexus 5020 which has a Mulitchassis Etherchannel to a pair of 6509s running VSS. The blade system is using HP Flex 10 cards*. My first issue that I ran into was that I had to enable Jumbo MTUs on the Nexus. The reason being is the HP Flex 10 cards where sending jumbo frames which were getting dropped I also had to enable Jumbo Frames on the the trunk ports as well as the ethernet ports on the VSS that connect back to the Nexus since there will be some inter-vlan routing going on. I guess I should enable jumbomtu on the layer 3 interfaces as well now that I think about it.

Do I also need to enable system jumbomtu on the VSS? What about the VSL links? The reason I ask is that when I run the command “show interface counter errors” I see giant frame errors on the VSL links as well as FCS errors. However, I cannot adjust the MTU size on the VSL links or the port channels since they are not switchports. Can I make the VSL links switchports or will VSS not allow this? I guess I’m a bit confused on the whole jumbomtu thing. Once you start to enable it where do you stop.

Thanks for the help,
Mark

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