mtu — interface
Maximum transmission unit (MTU)
Depends on media type (defaults for some common media are listed in Table 17-11, under the
ip mtu command)
This command allows you to modify the MTU for any interface. The default MTU depends on the media you are using (FDDI, Ethernet, etc.); for example, Ethernet has an MTU of 1,500.
Performance considerations may lead you to modify this value; a smaller MTU might give better performance on a lossy or noisy line.
interface ethernet0 mtu 1250