Administrator Guide

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, configure 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 configured. Assign the network address that is most
explicit first 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 first network address.
When configuring the network command, configure a network address and mask that is a superset of the IP subnet configured 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 specific 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 configure OSPFv2 on each interface (configure 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.
NOTE:
If using features like MD5 Authentication, ensure all the neighboring routers are also configured for MD5.
In the example below, an IP address is assigned to an interface and an OSPFv2 area is defined that includes the IP address of a Layer 3
interface.
The first bold lines assign an IP address to a Layer 3 interface, and theno shutdown command ensures that the interface is UP.
The second bold line assigns the IP address of an interface to an area.
Example of Enabling OSPFv2 and Assigning an Area to an Interface
Dell#(conf)#int te 4/44
Dell(conf-if-te-4/44)#ip address 10.10.10.10/24
Dell(conf-if-te-4/44)#no shutdown
Dell(conf-if-te-4/44)#ex
Dell(conf)#router ospf 1
Dell(conf-router_ospf-1)#network 1.2.3.4/24 area 0
Dell(conf-router_ospf-1)#network 10.10.10.10/24 area 1
Dell(conf-router_ospf-1)#network 20.20.20.20/24 area 2
Dell(conf-router_ospf-1)#
Dell#
Dell Networking recommends using the interface IP addresses for the OSPFv2 router ID for easier management and troubleshooting.
To view the configuration, use the show config command in CONFIGURATION ROUTER OSPF mode.
OSPF, by default, sends hello packets out to all physical interfaces assigned an IP address that is a subset of a network on which OSPF is
enabled.
To view currently active interfaces and the areas assigned to them, use the show ip ospf interface command.
Example of Viewing Active Interfaces and Assigned Areas
Dell>show ip ospf 1 interface
TengigabitEthernet 12/17 is up, line protocol is up
Internet Address 10.2.2.1/24, Area 0.0.0.0
Process ID 1, Router ID 11.1.2.1, Network Type BROADCAST, Cost: 1
Transmit Delay is 1 sec, State DR, Priority 1
Designated Router (ID) 11.1.2.1, Interface address 10.2.2.1
Backup Designated Router (ID) 0.0.0.0, Interface address 0.0.0.0
616
Open Shortest Path First (OSPFv2 and OSPFv3)