Configuring MTU on 9000 Series Switch

[BGPatemyHamster]

Hi All,

  We have a 6000 Series Switch with a vPC connected to a 9000 Series switch. So 6000 Series 2 ints in PC and 9000 Series 2 ints in same PC.

We are seeing input and giant errors on the 9000 series end, the 6000 AND 9000 series end is configured for MTU as follows as explained here:-

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

As these errors seem to usually be MTU related I read a bit further and noticed in the doc linked it states the following:-

Network QoS MTU Configuration
Nexus 3000: Includes Nexus 3048, 3064, 3132Q, 3132Q-X, 3132Q-XL, 3172, and 3500 Series switches
Nexus 5000: All Nexus 5000 and 5500 Series switches
Nexus 6000: All Nexus 6000 Series switches

In order to configure elevated MTU on these switches, create a network-qos policy or modify an existing policy in order to specify the elevated MTU. This configuration applies to all ports. This includes any Cisco Fabric Extender (FEX) ports connected to the switch. Per-port MTU is not supported.
policy-map type network-qos jumbo
  class type network-qos class-default
          mtu 9216
system qos
  service-policy type network-qos jumbo

Per-Port MTU Configuration
Nexus 3000: Includes Nexus 3132Q-V, 3164, 31108, 31128PQ, 3200 Series, and 36180YC-R switches
Neuxs 7000: All Nexus 7000- and 7700 Series switches
Nexus 9000: All Nexus 9200 Series switches (includes 92xxx), 9300 Series switches (includes 93xxx), and 9500 Series switches
In order to configure MTU on a per-port basis, this configuration is needed:
Nexus(config)#interface ethernet 1/1
Nexus(config-if)#mtu 9216

I note that the Network QoS MTU Configuration does not suggest the 9000 series can use the policy-map, rather that the 9000 series is Per-Port and should be configured per interface.

When I do a sh int on the interfaces connected to the port channel on the 9000 series to verify MTU size I do see that the MTU is showing as 1500, not 9216, however using show queuing on the 6000 series shows 9216 as configured MTU.

So am I correct in thinking I need to configure MTU on a per interface basis on the 9000 series?

[marce1000]

 Ref : https://www.cisco.com/c/en/us/support/docs/switches/nexus-9000-series-switches/118994-config-nexus-00.html

Per-Port MTU Configuration

Nexus 3000: Includes Nexus 3132Q-V, 3164, 31108, 31128PQ, 3200 Series, and 36180YC-R switches

Neuxs 7000: All Nexus 7000- and 7700 Series switches

Nexus 9000: All Nexus 9200 Series switches (includes 92xxx), 9300 Series switches (includes 93xxx), and 9500 Series switches

In order to configure MTU on a per-port basis, this configuration is needed:

Nexus(config)#interface ethernet 1/1
Nexus(config-if)#mtu 9216

[BGPatemyHamster]

Thanks, I perhaps didn't make myself clear. What I'm looking to understand is do you HAVE to do it on a per port basis? Or, like the 6000 series, can you configure a policy map globally?

[marce1000]

 - Check if this thread is helpful :

        https://community.cisco.com/t5/switching/nexus-9000-jumbo/td-p/3208761

 M.