Jumbo Frames over 10/100 link

Ricky S · ‎04-03-2012

Hi everyone,

I read that Jumbo frames, when enabled on Gig ingress interfaces on a switch, will be dropped if the egress interface is 10/100. Does this hold true if the actual egress interface on the switch is a gig interface however the port on the other end of that interface is 10/100 only such in a case of a PC. Would the frames still get dropped?

rizwanr74 · ‎04-03-2012

"Would the frames still get dropped?"

No. But it will fragment frames and which will cause high CPU utilization and delay.

Hope that answers your question.

thanks

cpembleton · ‎04-03-2012

Ricky,

Kinda depends on your switch/pc. There are some switches that have support for jumbo frames at 10/100. Like some of the line cards of a 6500. So if your switch supports jumbo on 10/100 and your host supports jumbo frame on 10/100 then no, nothing is dropped. Assuming the Jumbo value set is not larger than either side can support.

But if either the switch and/or pc doesn't then it will be dropped. Fragmentation only occurs over a layer3 boundry as long as the DF flag isn't set.

HTH

Thanks,

Chad

Ricky S · ‎04-04-2012

Hi gents, thanks for your responses. I am going to play around with this setting however since a switch reload is required after turning it on, I will have to wait for a window. I'll update this thread with the results.