# Configuring the MTU Size for Bridged Ethernet

You can use the bridge1483 mtu command to configure a nondefault maximum transmission unit (MTU) size, in bytes, for a bridged Ethernet interface. The default MTU size for a bridged Ethernet interface is 1518 bytes.

Because you configure a bridged Ethernet interface over an ATM 1483 subinterface, the MTU size set with the bridge1483 mtu command is limited by the MTU set for the underlying ATM 1483 subinterface. As a result, the bridge1483 mtu command requires you to configure an MTU size for the bridged Ethernet interface that does not exceed the maximum allowable MTU size for the underlying ATM 1483 subinterface, 9180 bytes.

The configured MTU size for an interface is referred to as its administrative MTU, and the MTU size at which the interface actually operates is referred to as its operational MTU. For bridged Ethernet interfaces, the operational MTU is the lesser of the following two values:

- The administrative MTU of the bridged Ethernet interface
- The administrative MTU of the underlying ATM 1483 subinterface

You can also use the bridge1483 mtu command in a profile to configure a nondefault MTU size for a dynamic bridged Ethernet interface. For information, see Configuring a Dynamic Interface from a Profile in Configuring Dynamic Interfaces.

bridge1483 mtu

- Use to set the maximum allowable size, in bytes, of the MTU for bridged Ethernet interfaces.
- Specify an MTU size in the range 64–9180 bytes.
- Example
  host1(config-subif)#bridge1483 mtu 1684
- Use the no version to restore the default MTU size for bridged Ethernet interfaces, 1518 bytes.
- See bridge1483 mtu.