MTU

[parthrawat979]

I am getting this error while changing mtu size in cisco ios:
% Interface FastEthernet0/0 does not support user settable mtu.
I am using Cisco IOS Software, 7200 Software (C7200-ADVENTERPRISEK9-M), Version 15.5(2)XB, RELEASE SOFTWARE (fc1)

[Joseph W. Doherty]

Most likely the error message is correct, i.e. you cannot change that interface's MTU.

What might be settable is changing the interface's IPMTU.

[M02@rt37]

Hello @parthrawat979 

Fastethernet interfaces on platfrom c7200 don't support user settable mtu.

[parthrawat979]

Yeah, I can however change the mtu on an Gig interface successfully.

[M02@rt37]

Exactly sir.

If you were in mpls environnement it should be possible on Fa to tune mtu with tag-switching mtu command.

[Joseph W. Doherty]

Yeah, I can however change the mtu on an Gig interface successfully.

Different interface hardware, FE vs. gig although you might bump into this for same bandwidth interfaces too.

MTU depends on actual hardware capability and also whether software (IOS) supports all the hardware's capabilities.

If the interface supports jumbo Ethernet its MTU should be changeable, but even then what you can set MTU to may vary between different interface hardware.

[Giuseppe Larosa]

Hello @parthrawat979 ,

on a cisco 7200 there are hardware differences between built in  ( part of I/O controller)  ports like the fas0/0 and ports provided by Port Adapters .

Your GE port is likely provided by a  port adapter.

Hope to help

Giuseppe