Difference between interface mtu and ip mtu

sebastan_bach · ‎09-13-2006

hi all can some pls tell me the difference between interface mtu and ip mtu. the confusion i feel is when we set the physical mtu it going to affect the ip packets anyway right then why do we have the ip mtu option. can someone pls explain the difference between them .

regards

sebastan

Edison Ortiz · ‎09-13-2006

Sebastian,

They aren't the same.

The interface MTU will alter the MTU at the interface level and it will affect all packets, IP and non-IP (IPX, for instance).

The IP MTU will only affect IP packets.

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Thanks

tdrais · ‎09-13-2006

To add to edisons answer

Many interfaces will not accept the command to change the MTU so your only option is to use the IP MTU command to change it.

gpulos · ‎09-13-2006

the 'IP MTU' command sets the maximum transmission size of IP Packets sent on an interface.

(this is specific to IP packets only; this does not limit the maximum MTU of the interface for non-IP protocols/packets)

please see the following link for more info on the IP MTU command:

http://www.cisco.com/en/US/products/sw/iosswrel/ps1828/products_command_reference_chapter09186a00800b3ddc.html#wp1019345

the 'interface MTU' command sets the maximum transmission size of ANY packets sent on an interface or subinterface.

(this is only specific to the interface; any packets will be restricted by this maximum limit no matter what protocol)

please see the following link for more info on configuring MTU size per interface/subinterface:

http://www.cisco.com/en/US/products/sw/iosswrel/ps1831/products_configuration_guide_chapter09186a0080087ced.html#wp1002739