Administrator Guide

If you are using a Loopback interface, refer to Loopback Interfaces.
2 Enable the interface.
CONFIG-INTERFACE mode
no shutdown
3 Return to CONFIGURATION mode to enable the OSPFv2 process globally.
CONFIGURATION mode
router ospf process-id [vrf {vrf name}]
•
vrf name: enter the keyword VRF and the instance name to tie the OSPF instance to the VRF. All network commands under this
OSPF instance are later tied to the VRF instance.
The range is from 0 to 65535.
The OSPF process ID is the identifying number assigned to the OSPF process. The router ID is the IP address associated with the
OSPF process.
After the OSPF process and the VRF are tied together, the OSPF process ID cannot be used again in the system.
If you try to enter an OSPF process ID, or if you try to enable more OSPF processes than available Layer 3 interfaces, prior to
assigning an IP address to an interface and setting the no shutdown command, the following message displays:
C300(conf)#router ospf 1
% Error: No router ID available.
Assigning an OSPFv2 Area
After you enable OSPFv2, assign the interface to an OSPF area. Set up OSPF areas and enable OSPFv2 on an interface with the
network command.
You must have at least one AS area: Area 0. This is the backbone area. If your OSPF network contains more than one area, congure a
backbone area (Area ID 0.0.0.0). Any area besides Area 0 can have any number ID assigned to it.
The OSPFv2 process evaluates the network commands in the order they are congured. Assign the network address that is most explicit
rst to include all subnets of that address. For example, if you assign the network address 10.0.0.0 /8, you cannot assign the network
address 10.1.0.0 /16 because it is already included in the rst network address.
When conguring the network command, congure a network address and mask that is a superset of the IP subnet congured on the
Layer-3 interface for OSPFv2 to use.
You can assign the area in the following step by a number or with an IP interface address.
• Enable OSPFv2 on an interface and assign a network address range to a specic OSPF area.
CONFIG-ROUTER-OSPF-id mode
network ip-address mask area area-id
The IP Address Format is A.B.C.D/M.
The area ID range is from 0 to 65535 or A.B.C.D/M.
Enable OSPFv2 on Interfaces
Enable and congure OSPFv2 on each interface (congure for Layer 3 protocol), and not shutdown.
You can also assign OSPFv2 to a Loopback interface as a virtual interface.
OSPF functions and features, such as MD5 Authentication, Grace Period, Authentication Wait Time, are assigned on a per interface basis.
636
Open Shortest Path First (OSPFv2)