ip ospf area

Enables OSPFv2 on an interface.

Syntax

ip ospf area area-id | ip-addr

no ip ospf area

Command Default

Disabled.

Parameters

area-id: Area ID in decimal format. Valid values range from 1 through 2147483647.
ip-addr: Area ID in IP address format.

Modes

Interface subtype configuration mode

Usage Guidelines

The no form of the command disables OSPFv2 on the interface.

When configuring OSPF on a VE interface that will be applied to a GRE tunnel, the MTU configured in that VE is applied to the GRE tunnel and is used as the MTU for the tunnel. When configuring the MTU for the tunnel interface, the assigned MTU value takes into account the 24 bytes reserved for the GRE Tunnel Header. This 24 bytes is automatically reduced from the target MTU.

Note

The 24 bytes consists of a 20 Byte GRE Outer Header and a 4 Byte Outer IP Header.

For example, when the VE MTU is set to the default MTU 1500, the GRE tunnel MTU will automatically be adjusted to 1476 Bytes and the remaining 24 bytes are used to carry the GRE Tunnel Header information . If the VE MTU is set to any value other than the default MTU value, the reserved 24 bytes will be automatically reduced from your target configuration before it is set as the VE's MTU.

In the case where you want to assign the maximum permissible MTU of 9194 Bytes, you must manually reduce the reserved 24 Bytes. In this case, you should set the MTU value at 9170 Bytes.

Examples

The following example enables a configured OSPFv2 area named 1 on a specific OSPFv2 virtual Ethernet (VE) interface.

device# configure terminal
device(config)# interface ve 1
device(config-if-Ve-1)# ip ospf area 1