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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 EMC 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
Loopback interfaces also help the OSPF process. OSPF picks the highest interface address as the router-id and a Loopback
interface address has a higher precedence than other interface addresses.
Example of Viewing OSPF Status on a Loopback Interface
Configuring Stub Areas
OSPF supports different types of LSAs to help reduce the amount of router processing within the areas.
Type 5 LSAs are not flooded into stub areas; the ABR advertises a default route into the stub area to which it is attached. Stub
area routers use the default route to reach external destinations.
To ensure connectivity in your OSPFv2 network, never configure the backbone area as a stub area.
To configure a stub area, use the following commands.
1. Review all areas after they were configured to determine which areas are NOT receiving type 5 LSAs.
EXEC Privilege mode
show ip ospf process-id [vrf] database database-summary
2. Enter CONFIGURATION mode.
EXEC Privilege mode
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Open Shortest Path First (OSPFv2 and OSPFv3)