Help Understand Jumbo Frames

[dave cooper]

I was hoping to get help in understanding jumbo frames. I have the following setup in our network. If host 1 sends a jumbo frame to host 2 what will happen on the switch. The SVI VLAN 10 has the MTU of 9216 and the SVI VLAN 11 MTU is 1518. Will the switch fragment the packet to 1518 bytes when it send the traffic to host 2?

[Charles Hill · Accepted solution]

Hey Dave,

When a jumbo frame traverses only layer 2, it will be dropped.

When a jumbo frame is routed, it will be fragmented.(unless the df bit is set, in which case it's dropped)

The posting below discusses jumbo frames in detail.

https://supportforums.cisco.com/discussion/11399941/does-jumbo-frames-ever-get-fragmented

Hope this helps,

Please rate helpful answers.

Thanks.

[Joseph W. Doherty]

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting
As your OP described two VLANs, which usually implies different subnets, and the need to route between them, Charles' second sentence would apply.

[dave cooper]

Thanks For the information.

Much appreciated