*****Jumbo frame on colapse core****

[Jean Paul Enerst]

Hi Folks,

I have been thinking and research about for that a while now, and yet i have not gotten a formal answer... Please read carefully...

We are a medium size company.... In both our our remotes, we have four 3750G(two of them are 3750X) in a stack. All good there, the nightmare is we have everything single thing(pc,printer,phones,ipcam,servers(running esxi),SAN(storageFlex)) connected to the stack;therefore, the stack switches are acting as core,distribution and access layer at the same time.

I need to enable jumbo frame to speed up back, isci frame between SAN and ESXi hosts. knowing i can only enable jumbo frame globally. Since i have all these devices connected to the stack which aren't supported jumbo! should i go head enable jumbo on the stack? Will the device which aren't support jumbo frame will continue to work? Or since i know interface with 100Mb and less will ignore jumbo, should i set all device for which i don't jumbo frame to 100Mb?

Any help and suggestion will be greatly appreciate.

Thanks,

[Joseph W. Doherty]

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Posting

A device that doesn't support jumbo on a port that does, will work fine as long as another device doesn't send it a jumbo frame.  If that happens, the device will be unable to process the received jumbo frame.  (I.e. a jumbo enabled switch can allow MTU mismatch between hosts.)

(If you're thinking about IP fragmentation, that will only happen across a L3 hop, and it often creates additional performance issues.)

BTW, on the 3750 series, data transfer performance problems are often caused by default 3750 buffer allocations.  Allowing jumbo doesn't address that.  I.e., you might obtain much be better data transfer performance via buffer tuning.