Configuring Open Shortest Path First (OSPF) Protocol

Open Shortest Path First (OSPF) Protocol

OSPF is a Link State protocol that’s considered may be the most famous protocol among the Interior Gateway Protocol (IGP) family, developed in the mid 1980’s by the OSPF working group of the IETF.

When configured, OSPF will listen to neighbors and gather all link state data available to build a topology map of all available paths in its network and then save the information in its topology  database, also known as its Link-State Database (LSDB). Using the information from its topology database. From the information gathered, it will calculate the best shortest path to each reachable subnet/network using an algorithm called Shortest Path First (SFP) that was developed by the computer scientist Edsger W. Dijkstra in 1956. OSPF will then construct three tables to store the following information:

• Neighbor Table: Contains all discovered OSPF neighbors  with whom routing information will be interchanged
• Topology Table: Contains the entire road map of the network with all available OSPF routers and calculated best and alternative paths.
• Routing Table: Contain the current working best paths that will be used to forward data traffic between neighbors.

Steps:

1) Initially connect all three PCs with routers and switches. Then connect all the routers with      each other. Make all the necessary connections.

2) Assign IP Addresses, Subnet Mask and Gateway as follows:-

Network-1

    Router-1     192.168.2.2     255.255.255.0             ---

    PC-1           192.168.2.1     255.255.255.0      192.168.2.2

Network-2

    Router-2     192.168.3.2     255.255.255.0             ---

    PC-2           192.168.3.1     255.255.255.0      192.168.3.2

Network-3

    Router-3     192.168.6.2     255.255.255.0             ---

    PC-3           192.168.6.1     255.255.255.0      192.168.6.2

Network-4

    Router-1     192.168.4.1     255.255.255.0             ---

    Router-2     192.168.4.2     255.255.255.0             ---

Network-5

    Router-2     192.168.5.1     255.255.255.0             ---

    Router-3     192.168.5.2     255.255.255.0             ---

Network-6

    Router-1     192.168.1.1     255.255.255.0             ---

    Router-3     192.168.1.2     255.255.255.0             ---

3) Now after all the connections and configuring the IPs, Subnet and Gateways of the                connecting device, go to the CLI of the routers and type the command-

    #router ospf 10

    Here 10 is the process ID of the OSPF protocol. 

4) Now type network Networkid_ip wildcard mask area no.

e.g: network 192.168.1.0   0.010.255   area 0. 

5) Now Ping to check.

Router Commands

Router(Config-if) #ip address 192.168.3.2    255.255.255.0

Router(Config-if) #exit

Router(Config) #interface Serial 0/0/0

Router(Config-if) #if address 192.168.1.2    255.255.255.0

Router(Config) #interface gigabit ethernet 0/0

Router(Config-if) #no shut exit

Router(Config) #router

Router(Config-router) #network   192.168.1.0   0.0.0.255   area0

Router(Config-router) #network   192.168.3.0   0.0.0.255   area0

Router(Config-router) #exit