ADTRAN 1000R Series

Command Reference Guide Loopback Interface Configuration Command Set

mtu <size>

Use the mtu command to configure the maximum transmit unit size for the active interface. Use the no

form of this command to return to the default value.

Syntax Description

<size> Configures the window size for transm itted packets. The valid ranges for the

various interface s ar e listed be low:

ATM interfaces 64 to 1520

Demand interfaces 64 to 1520

Ethernet interfaces 64 to 1500

FDL interfaces 64 to 256

HDLC interfaces 64 to 1520

Loopback interfaces 64 to 1500

Tunnel interfaces 64 to 18,190

Virtual Frame Relay sub-interfaces 64 to 1520

Virtual PPP interfaces 64 to 1500

Default Values

<size> The default values for the various interfaces are listed below:

ATM inter faces 1500

Demand interfaces 1500

Ethernet interfaces 1500

FDL interfaces 256

HDLC interfaces 1500

Loopback interfaces 1500

Tunnel interfac es 1500

Virtual Frame Relay sub-interfaces 1500

Virtual PPP interfaces 1500

Applicable Platforms

This command applies to the NetVanta 300, 1000, 1000R, 2000, 3000, 4000, and 5000 and

Total Access 900 Series units.

Command History

Release 1.1 Command was introduced.

Functional Notes

OSPF will not become adjacent on links where the MTU sizes do not match. If router A and router B are

exchanging hello packets but their MTU sizes do not match, they will never reach adjacency. This is by

design and required by the RFC.

Usage Examples

The following example specifies an MTU of 1200 on the loopback interface:

(config)#interface loopback 1

(config-loop 1)#mtu 1200