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Discussion on Jumbo frames and Virtual Connect stats

Trusted Contributor

Discussion on Jumbo frames and Virtual Connect stats

A question on Ethernet jumbo frames from Mike:




I just wanted to ask a question about Virtual Connect:


Is there an easy way to find out whether Jumbo Frames is enabled or disabled on the VC modules?

I know by default it’s supposedly enabled, but I want to check.




From Robert:

It is enabled by default, and cannot be disabled.  It is listed in the QuickSpecs.


From Mark:

This is low-level chip functionality. There are no controls to disable Jumbo Frames, and you are correct it is enabled by default and forever.

Support dump, NETSERVE_se_Dump would show frame size on a port basis = 9216

The other thing that might be confusing is the jumbo frames counters for ports on VC was fixed in VC 4.20. So even though Jumbo Frames are working, the counters would be 0.

Frames larger than 1518 not counted as StatsOversizePackets was fixed in VC 3.61 (For 1/10 1/10-F) and VC 4.20 (for all other modules).



Input from Rick:

If jumboframes are enabled, I would think that frames larger than 1518 would not be "Oversize."  Oversize in the name implies an error.


Reply from Mark:

The source is this is a Broadcom terminology, rather right or wrong.

The VC Module has a Broadcom ASIC.

Many HP NICs have Broadcom ASICS.


HP NICs use this on Advanced Properties:


Jumbo MTU. The Jumbo MTU property allows the network adapter to transmit and receive oversized Ethernet frames that are greater than 1514 bytes, but less than or equal to 9000 bytes in length. This property requires the presence of a switch that is able to process jumbo frames.




Other comments or questions?