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Beginner

ip mtu on 3750/3650x ports

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.

3 REPLIES 3
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Hall of Fame Expert

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

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Advisor

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.

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

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