tstanik Wed, 09/03/2008 - 10:36
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Configurable maximum transmission unit (MTU) of up to 9000 bytes, for bridging on Gigabit Ethernet ports, and up to 1998 bytes for bridging and routing on Fast Ethernet ports for Cisco ME 3400 Series Ethernet Access Switches.

patricia20 Wed, 09/03/2008 - 12:39
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Yup, I've read this one from the documentation. Hmm, just wondering what would be the MTU for routing of Gigabit Ethernet ports? Cause it only states there the bridging for GE ports. Would there also be a value for routing?


william.caban Thu, 09/04/2008 - 02:39
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The routing mtu is 1500 bytes by default. You may change it globally in this switches using the "system mtu routing " global command.

You may verify your current setup like this:

Switch# show system mtu

System MTU size is 1500 bytes

System Jumbo MTU size is 1500 bytes

Routing MTU size is 1500 bytes

For more information on setting the routing MTU, take a look to this URL.




patricia20 Thu, 09/04/2008 - 12:36
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Looking at the link, it says that the range for routing bytes is 1500 bytes to the 'system MTU value', where system routing MTU is the max MTU for routed packets. Is there a defined value for this max MTU? Sorry to bother you with this but since we don't have an ME3400 yet, I won't be able to see the possible range from the CLI. We're still checking if this will fit our requirement.


linuxloader Sun, 09/14/2008 - 13:17
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c3400-ME#sh system mtu

System MTU size is 1600 bytes

System Jumbo MTU size is 9000 bytes

Routing MTU size is 1600 bytes

The routing mtu is the max of the system mtu , it`s changed global and can`t be changed per vlan int or other int , jumbo frames are anabled only for gig intefeices , "jumbo" mtu ot non gig interfaces is needed in most cases for qinq


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