Enabling Jumbo Frame on N7K with FEX attached

[dtran]

Hi all,

I have a pair of N7K's in vPC topology with some FEXs attached. I am looking into enabling Jumbo frame on the N7K as well as the FEX. I understand Jumbo frame is enabled globally by default. My question is I have some interfaces in a port-channel that I need jumbo frame enabled. Do I enable it at the port-channel interface or at the physical interface ? and is the change disruptive to the network ?

I am running NX-OS 6.0.2

thanks all in advance !! I appreciate any inputs/suggestions !!

D.

[Reza Sharifi]

Hi,

On the Nexus 7Ks, you need to enable it globally first and than raise the MTU on the Portchannel and not the physical interface. If you have OSPF, BGP, etc.. peering, it will be disruptive, so I would recommend having an outage window to do this, just in case. 

On the 5Ks, it is completly a different story.

HTH

[dtran]

Hi Reza !! Thanks for your help !!!

I know jumbo frame is enabled on the N7K by default. Do you have the procedure on how to enable jumbo frame on the port-channel ?

D.

[Reza Sharifi]

Hi D,

It is very simple.

First enable is globally

system jumbomtu 9216

than go under the portchannel interface

example

inter po120

mtu 9216

That is all you need

than do a "sh int po120" to verify it.

You can also use the same command to verify all the physical interfaces belonging to that portchannel.

http://www.cisco.com/en/US/docs/switches/datacenter/sw/5_x/nx-os/interfaces/command/reference/if_commands.html#wp1689829

HTH

Reza

[dtran]

Reza,

Questions:

For Nexus 7010's in vPC topology, if I enable jumbo frame on the interface. Do I need to enable jumbo frame on the vPC peer-link for jumbo packets that need to traverse across the vPC peer-link ?

Thanks Reza !!

D.

[Reza Sharifi]

Dan,

No need to. Jumbo frames are enabled by default on the vPC peer link.

http://www.cisco.com/en/US/docs/switches/datacenter/sw/4_2/nx-os/interfaces/configuration/guide/if_vPC.html#wp1559816

HTH

Reza

[dtran]

Hi Reza,

You positive that Jumbo frame is enabled by default on vPC peer-link ? I looked through the link you sent but don't see where it said vPC is enabled by default on vPC peer-link.

Do you typically enable Jumbo frame on 10gig link ?

when you enable jumbo frame on an interface you're basically allowing that interface to accept frames that are larger than 1500 byte but it still accepts frames that are 1500 bytes or smaller as well correct ?

Thanks Reza !!

D.