Setting MTU on C9300

[jmcgrady1]

I have a C9300-24T which needs to have its IOS updated. Its currently running v16.12.4.  In the meantime, i need to set the MTU size on a switch interface. The usual "mtu xxxx" and "ip mtu xxxx" commands appear to be missing/invalid. Do you know what the equivalent commands were fro this IOS version?

[Leo Laohoo]

Interface-level MTU is not supported on the 9300.  

[M02@rt37]

Hello @jmcgrady1 

C9300 does not support the MTU on a per-interface basis. If you enter the system mtu bytes command in global configuration mode, the command affects all the switched and routed ports on that switch.

You should use system mtu command, see references here:

https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst9300/software/release/16-12/configuration_guide/int_hw/b_1612_int_and_hw_9300_cg/configuring_system_mtu.html

[Jens Albrecht]

Hello @jmcgrady1,

in case of the Catalyst 9300 series your options depend on the interface type.

Regarding the System MTU, these devices does not support the MTU on a per-interface basis.
So the System MTU can only be set globally.

However, you can configure a Protocol-Specific MTU to override system MTU values on routed interfaces.

So you can configure the protocol-specific MTU under each routed interface with the 'ip mtu <size>' and 'ipv6 mtu <size>' commands. Of course, this value cannot exceed the global system mtu size.

You can find references and config examples at the Interface and Hardware Components Configuration Guide, Cisco IOS XE Gibraltar 16.11.x (Catalyst 9300 Switches).

HTH!