How to Configure OSPF Backbone Area | How to Configure OSPF Area 0

OSPF is a widely used dynamic routing protocol. It is an open standard protocol, meaning that any router will support it. It uses a link-state algorithm to dynamically learn the route to every subnet existing in a single autonomous system.

In a multi-area OSPF network, the backbone area (Area 0) obtains the summarized route from the area border routers and aggregates this traffic to be routed to the non-OSPF network.

Also, the ABRs provide a summarized route from the backbone area to other OSPF areas existing on the network.

Usually, edge routers connecting the autonomous system to other autonomous systems are attached to the backbone area. This makes the backbone area the highest-level OSPF area for a specific autonomous system.

When grouping the routers that will form the OSPF backbone area, it must be done in a way that at least one area border router connects it to other OSPF areas existing in that specific autonomous system.

In this post, I will show you how to configure the OSPF backbone area.

Network Topology

The network topology we will be making use of in this post is shown below. As you can see, it consists of three routers. In this demonstration, we will configure the OSPF backbone area on the three routers.

How to Configure the OSPF Backbone Area

The process to configure OSPF Backbone Area is simple; just configure the OSPF process ID on each of the backbone routers and then advertise the networks attached to the interface of the backbone routers.

Here are the steps to configure the OSPF backbone area.

Step 1: Configure the interface of the backbone routers.

The first step is to assign an IP address to the interfaces of the backbone routers.

For the network topology we are using, the interface configuration is as follows:

Router 1

R1(config)#interface ethernet0/0
R1(config-if)#ip address 192.168.12.1 255.255.255.0
R1(config-if)#no shutdown 
R1(config-if)#exit

R1(config)#interface loopback 0
R1(config-if)#ip address 1.1.1.1 255.255.255.0
R1(config-if)#no shutdown 
R1(config-if)#exit

Router 2

R2(config)#interface ethernet0/0
R2(config-if)#ip address 192.168.12.2 255.255.255.0
R2(config-if)#no shutdown 
R2(config-if)#exit

R2(config)#interface ethernet0/1
R2(config-if)#ip address 192.168.23.1 255.255.255.0
R2(config-if)#no shutdown 
R2(config-if)#exit

Router 3

R3(config)#interface ethernet0/0
R3(config-if)#ip address 192.168.23.2 255.255.255.0
R3(config-if)#no shutdown
R3(config-if)#exit

R3(config)#interface loopback 0
R3(config-if)#ip address 3.3.3.3 255.255.255.0
R3(config-if)#no shutdown 
R3(config-if)#exit

Step 2: Configure OSPF on the backbone routers.

The backbone Routers are the routers that are inside or partially inside the OSPF Backbone Area. For the above topology, Router 1, Router 2, and Router 3 are the backbone routers.

Router 1

R1(config)#router ospf 1 
R1(config-router)#router-id 1.1.1.1
R1(config-router)#network 192.168.12.0 0.0.0.255 area 0
R1(config-router)#network 1.1.1.0 255.255.255.0 area 0
R1(config-router)#exit

Router 2

R2(config)#router ospf 1
R2(config-router)#network 192.168.12.0 0.0.0.255 area 0
R2(config-router)#network 192.168.23.0 0.0.0.255 area 0
R2(config-router)#exit

Router 3

R3(config)#router ospf 1
R3(config-router)#network 192.168.23.0 0.0.0.255 area 0
R3(config-router)#network 3.3.3.0 0.0.0.255 area 0     
R3(config-router)#exit

Step 3: Test the OSPF Configuration

To confirm that the configuration is working perfect, ping from one backbone Router to another.

R1#ping 3.3.3.3 source 1.1.1.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 3.3.3.3, timeout is 2 seconds:
Packet sent with a source address of 1.1.1.1 
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/1 ms

R3#ping 1.1.1.1 source 3.3.3.3
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 1.1.1.1, timeout is 2 seconds:
Packet sent with a source address of 3.3.3.3 
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/1 ms

Related Content;

1. How to Configure OSPF Default Route on a Cisco Router
2. How to Configure OSPF DR and BDR
3. How to Configure OSPF Passive Interface on Cisco Router
4. Configuring OSPF Hello Timer
5. How to Configure OSPF Multi-Area
6. How To Configure OSPF on Layer 3 Switch In Packet Tracer
7. Redistributing Static Routes into OSPF: Explained With Example

Reference: https://github.com/misterkrittin/CCNA-Labs