ONTAP Discussions

multimode VIF trunk with with vlans in different broadcast domains with differing MTU sizes


Is this a valid configuration for multiple tagged VLAN's with differing MTU sizes?


Use Case:


a single multimode VIF trunk (a0a w/ member ports e0e,e0f) at 9000 MTU.

On the trunk there are two tagged vlans, NFS vlan (a0a-111) in a broadcast domain with 9000 MTU and a CIFS vlan (a0a-110) in a different broadcast domain with 1500 MTU.

a0a is not in any broadcast domain. Only tagged VLANS are in broadcast domains.


Broadcast Domain: NFS
MTU: 9000


Broadcast Domain: CIFS
MTU: 1500


IFGRP: a0a
Member Ports: e0e e0f


Tagged VLAN: a0a-110
Broadcast Domain: CIFS

Tagged VLAN: a0a-111
Broadcast Domain: NFS




That looks reasonable - the main challenge is if you had an ifgrp designated at a lower MTU than the packets you'd be sending it (i.e. resulting in fragmentation).  Any reason reason why you don't just mark the CIFS broadcast domain as 9K?  Since your filer is just a CIFS "target" it's not like it's going to be trying to initiate sending jumbo-frames to something else that wouldn't be able to handle the traffic without fragmenting (unless I'm misrepresenting/misunderstanding your environment).  Then it would just process any traffic up to and including MTU 9K without issues...


My other observation is to make sure that you have your ifgrp ports designated such that they are spanning different ASICs within the controller.  See page page 12 of TR-4182:




On our FAS8040s that translates into us creating our ifgrp on ports e0e and e0g.


Hope that helps,