I had a question, why am I able to configure the MTU on a FastEthernet between 9216-9216? Is the MTU parameter under the copper interface meaning something else? Usually its between 1480 and 1524.
show run int fast 4/31
int fast 4/31
<9216-9216> MTU size in bytes
show int fast 4/31 status
Port Name Status Vlan Duplex Speed Type
Fa4/31 notconnect 1 full 100 10/100BaseTX
It appears that the mtu size command is in reference to egress traffic on a FastEthernet port.
See the config guide for 12.2(SXH)
Configuring a nondefault MTU size on a 10, 10/100, or 100 Mbps Ethernet port limits ingress packets to the global LAN port MTU size and permits egress traffic of any size larger than 64 bytes.