Implementing jumbo frames on Nexus 7K and 5K

[Zeeshan Siddiqui]

Can you please assist with the following

In the past I have applied jumbo frames on Nexus 5K and 7K only during initial installs and not when they are in production.please find my questions below  (you help is much appreciated)

Nexus 5K

For the Nexus 5K I am planning to implement the config below, on the same Nexus 5596 half the interfaces are running Native FC  (Not FCOE) and the switch is on 6.2 making an MTU change  inconsistancy 2 and not 1, will I see any impact on the interfaces running native FC or will they just ignore the config as they are FC ports ?

policy-map type network-qos jumbo
  class type network-qos class-default
    mtu 9216
system qos
  service-policy type network-qos jumbo

Nexus 7K

Nexus 7K config:   

Is there an impact of running the system jumbomtu 9216 command with regards to service disruption  ?     (we are doing it out of hours)

Even though we have the system jumbomtu 9216 command we are only enabling it on one ethernet interface and one SVI as per example below ?

system jumbomtu 9216

!

interface ethernet x/y
mtu 9216

interface vlan xxx
mtu 9216

Thanks,

Zee

[Zeeshan Siddiqui]

Need some Help  here please

Thanks,

Zee
 

[Reza Sharifi]

You would need to do it in a maintenance window as changing the MTU size can disrupt traffic specially when you deploy it on physical interfaces.  If you are planning on enabling it on a physical interface it needs to be a layer-3 interface

http://www.cisco.com/c/en/us/td/docs/switches/datacenter/sw/5_x/nx-os/interfaces/configuration/guide/if_cli/if_basic.html#pgfId-1327529

HTH

[Zeeshan Siddiqui]

Hi Reza,

For the physical interfaces on the Nexus 7K we will do it at the same time to avoid an inconsistancy 1 issue for the portchannels.

And enable mtu 9216 on the SVI where we need to route jumbo frames between SVI.

With regards to the  Nexus 5K as the QOS policy is a global one will it have any impact on FC interfaces running of the same switch  (I reken the global policy will only take affect for ethernet ports and will not affect FC ports)

Kind Regards,

Zee

[Reza Sharifi]

Hi,

I don't think it is going to have any effect on FC ports as you can't modify the MTU for fiber channel interfaces.

from the config guide;

The FCoE system class (for Fibre Channel and FCoE traffic) has a default MTU of 2240 bytes. This value cannot be modified.

link:

http://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus5000/sw/qos/b_Cisco_Nexus_5000_Series_NX-OS_Quality_of_Service_Configuration_Guide/Cisco_Nexus_5000_Series_NX-OS_Quality_of_Service_Configuration_Guide_chapter3.html

HTH