ip mtu on 3750/3650x ports

[tarekaljallad]

I'm not able to set the mtu on an SVI or routed gigabit port on either model. they are running 12.2(55)SE4.

It comes back as "% ip mtu is not supported on this interface".

Anyone know why?

Also, is there any reason why when the "ip tcp adjust-mss", (set to lower than default) is applied to the egress SVI on a 3750 or 3560x, the mms value of the SYN packet is not adjusted when captured at the receiving end? It seems as if the setting does nothing.

[Reza Sharifi]

The MTU value for 3560s and 3750s series must be set globally and not under the interface.

use command

system mtu

Switch(config)#system mtu ?      

  <1500-1998>  MTU size in bytes

  jumbo        Set Jumbo MTU value for GigabitEthernet or TenGigabitEthernet

               interfaces

  routing      Set the Routing MTU for the system

Switch(config)#system mtu

HTH

[glen.grant]

Due to hardware limitations on the 3x50 series  any routable interface cannot run jumbo frames so any frame that has to be routed off it's current subnet will be fragmented.

[tarekaljallad]

So its safe to say that both commands are not valid on the 3750 and 3560s?