cancel
Showing results for 
Search instead for 
Did you mean: 
cancel
1531
Views
0
Helpful
1
Replies

Ramifications of setting MTU 9000

robert.parsons
Level 1
Level 1

I have 4 Cisco 3750's layer 2/3 in a stack that is used for server and core connectivity. There are 3 VLAN's for a hyperv cluster, one for iscsi traffic, one for heartbeat/live migration cluster traffic and one for a virtual switch and all other servers on the network. I want an MTU of 9000 for the iscsi traffic and heartbeat/live migration but it appears the MTU setting needs to be global, per interface is not supported.

Will setting the MTU to 9000 cause any issues with the other servers on the stack?

1 Reply 1

Joseph W. Doherty
Hall of Fame
Hall of Fame

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

It might.

Other hosts using standard sized MTU on jumbo enabled links won't care.  The possible issue is, the 3750 can share egress buffers in its common pool.  Jumbo Ethernet will consume more RAM per jumbo frame.  So it's possible, RAM buffer resources might no longer available for non-jumbo flows.

I wouldn't think it will be a big difference, because overall transmission volume shouldn't be that different, but the larger frames will, by reducing overhead, allow a slightly higher effective transmission rate.  It also eases the load on server NICs allowing them to easier to hit full wire-rate.

Review Cisco Networking for a $25 gift card