Open Shortest Path First
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OSPF (Open Shortest Path First) is a link-state routing protocol that uses the Dijkstra algorithm to determine the shortest path for data packets. It supports hierarchical routing with areas, which makes it scalable for large networks. OSPF is an open standard protocol, which means it can be used across various vendor devices.
Key features of OSPF include:
- Fast Convergence: Quickly adapts to changes in the network topology.
- Scalability: Supports large and complex networks through the use of areas.
- VLSM and CIDR Support: Allows for efficient use of IP address space.
Configuration Commands
Router OSPF
Enters router configuration mode for an OSPF process. The process-id is a locally significant identifier for the OSPF process.
Syntax:
router ospf [process-id]
Example:
Router1>enable
Router1#configure terminal
Router1(config)#router ospf 1
Network
Defines which interfaces run OSPF and specifies the area they belong to. The network command uses wildcard masks to match IP addresses.
Syntax:
network [address] [wildcard-mask] area [area-id]
[address]: The IP address or range that OSPF should run on.[wildcard-mask]: The inverse of the subnet mask, used to match the network.[area-id]: The OSPF area identifier.
Example:
Router1>enable
Router1#configure terminal
Router1(config)#router ospf 1
Router1(config-router)#network 192.168.1.0 0.0.0.255 area 0
IP Address
Assigns an IP address to an interface. This is necessary for the interface to participate in OSPF.
Syntax:
ip address [ip-address] [subnet-mask]
Example:
Router1>enable
Router1#configure terminal
Router1(config)#interface FastEthernet 0/1
Router1(config-if)#ip address 192.168.1.1 255.255.255.0
No Shutdown
Enables an interface that was previously shut down, making it active and allowing it to participate in OSPF.
Syntax:
no shutdown
Example:
Router1>enable
Router1#configure terminal
Router1(config)#interface FastEthernet 0/1
Router1(config-if)#ip address 192.168.1.1 255.255.255.0
Router1(config-if)#no shutdown
Verification and Troubleshooting
Show IP OSPF Interface
Displays OSPF information for interfaces, including their state, timers, and OSPF neighbors.
Syntax:
show ip ospf interface
Example:
Router1>enable
Router1#show ip ospf interface
Show IP OSPF Neighbor
Displays OSPF neighbor information, showing the status of OSPF neighbors and the state of OSPF adjacency.
Syntax:
show ip ospf neighbor
Example:
Router1>enable
Router1#show ip ospf neighbor
Show IP Route
Displays the IP routing table, including routes learned via OSPF.
Syntax:
show ip route
Example:
Router1>enable
Router1#show ip route
Output Example:
O 192.168.2.0/24 [110/2] via 192.168.1.2, 00:01:23, FastEthernet0/0
EVE-NG Lab
This lab will guide you through configuring the OSPF (Open Shortest Path First) routing protocol on Cisco routers. You will learn how to configure OSPF to enable dynamic routing within a network, ensuring that different routers can communicate effectively.
| Device | Interface | IP Address | Subnet Mask |
|---|---|---|---|
|
Router1 |
Fa0/0 |
10.1.1.1 |
255.255.255.0 |
|
Router1 |
S0/0 |
172.16.10.1 |
255.255.255.0 |
|
Router2 |
Fa0/0 |
10.1.1.2 |
255.255.255.0 |
|
Router4 |
S0/0 |
172.16.10.2 |
255.255.255.0 |
Basic Settings
Configure Interfaces
Router 1
Router>enable
Router#configure terminal
Router(config)#hostname Router1
Router1(config)#interface FastEthernet 0/0
Router1(config-if)#ip address 10.1.1.1 255.255.255.0
Router1(config-if)#no shutdown
Router1(config-if)#interface Serial 0/0
Router1(config-if)#ip address 172.16.10.1 255.255.255.0
Router1(config-if)#clock rate 64000
Router1(config-if)#no shutdown
Router1(config-if)#interface Serial 0/1
Router1(config-if)#ip address 172.16.11.1 255.255.255.0
Router1(config-if)#no shutdown
Router1(config-if)#interface FastEthernet 0/1
Router1(config-if)#ip address 10.1.2.1 255.255.255.0
Router1(config-if)#no shutdown
Router1(config-if)#end
Router 2
Router>enable
Router#configure terminal
Router(config)#hostname Router2
Router2(config)#interface FastEthernet 0/0
Router2(config-if)#ip address 10.1.1.2 255.255.255.0
Router2(config-if)#no shutdown
Router2(config-if)#end
Router 4
Router>enable
Router#configure terminal
Router(config)#hostname Router4
Router4(config)#interface Serial 0/0
Router4(config-if)#ip address 172.16.10.2 255.255.255.0
Router4(config-if)#no shutdown
Router4(config-if)#interface FastEthernet 0/0
Router4(config-if)#ip address 192.168.1.1 255.255.255.0
Router4(config-if)#no shutdown
Router4(config-if)#end
Router 5
Router>enable
Router#configure terminal
Router(config)#hostname Router5
Router5(config)#interface Serial 0/0
Router5(config-if)#ip address 172.16.11.2 255.255.255.0
Router5(config-if)#no shutdown
Router5(config-if)#interface FastEthernet 0/0
Router5(config-if)#ip address 192.168.2.1 255.255.255.0
Router5(config-if)#no shutdown
Router5(config-if)#end
Router 3
Router>enable
Router#configure terminal
Router(config)#hostname Router3
Router3(config)#interface FastEthernet 0/0
Router3(config-if)#ip address 10.1.2.2 255.255.255.0
Router3(config-if)#no shutdown
Router3(config-if)#end
Configuring OSPF
Router 1
Configure OSPF
Enter OSPF Router Configuration Mode:
Router1(config)#router ospf 1
Router1(config-router)#
Define OSPF Networks
Add FastEthernet 0/0 Network:
Router1(config-router)#network 10.1.1.0 0.0.0.255 area 0
Add FastEthernet 0/1 Network:
Router1(config-router)#network 10.1.2.0 0.0.0.255 area 0
Add Serial 0/0 Network:
Router1(config-router)#network 172.16.10.0 0.0.0.255 area 0
Add Serial 0/1 Network:
Router1(config-router)#network 172.16.11.0 0.0.0.255 area 0
Explanation: The network command specifies which interfaces will participate in OSPF. The wildcard mask (0.0.0.255 for /24) and area 0 indicate the OSPF area.
Router 2
Configure OSPF
Enter OSPF Router Configuration Mode:
Router2(config)#router ospf 1
Router2(config-router)#
Define OSPF Network
Add FastEthernet 0/0 Network:
Router2(config-router)#network 10.1.1.0 0.0.0.255 area 0
Router2(config-router)#end
Router 4
Configure OSPF
Enter OSPF Router Configuration Mode:
Router4(config)#router ospf 1
Router4(config-router)#
Define OSPF Network
Add Serial 0/0 Network:
Router4(config-router)#network 172.16.10.0 0.0.0.255 area 0
Add FastEthernet 0/0 Network:
Router4(config-router)#network 192.168.1.0 0.0.0.255 area 0
Router 5
Configure OSPF
Enter OSPF Router Configuration Mode:
Router5(config)#router ospf 1
Router5(config-router)#
Define OSPF Networks:
Add Serial 0/0 Network:
Router5(config-router)#network 172.16.11.0 0.0.0.255 area 0
Add FastEthernet 0/0 Network:
Router5(config-router)#network 192.168.2.0 0.0.0.255 area 0
Router 3
Configure OSPF
Enter OSPF Router Configuration Mode:
Router3(config)#router ospf 1
Router3(config-router)#
Define OSPF Network:
Enter OSPF Router Configuration Mode:
Router3(config-router)#network 10.1.2.0 0.0.0.255 area 0
Verifying OSPF Configuration
Verify OSPF Neighbors
Show OSPF Neighbors
Show OSPF Neighbors on Router1:
Router1#show ip ospf neighbor
Expected Output:
sqlCopy code
Neighbor ID Pri State Dead Time Address Interface
172.16.10.2 1 FULL/DR 00:00:32 172.16.10.2 Serial0/0
10.1.1.2 1 FULL/BDR 00:00:32 10.1.1.2 FastEthernet0/0
...
Verify OSPF Routes
Show IP Route
Show IP Route on Router1:
Router1#show ip route
Expected Output:
pythonCopy code
O 10.1.2.0/24 [110/2] via 172.16.10.2, 00:00:32, Serial0/0
...
Verify OSPF Process
Show IP Protocols
Show OSPF Process on Router1:
Router1#show ip protocols
Expected Output:
pythonCopy code
Routing Protocol is "ospf 1"
Outgoing update filter list for all interfaces is not set
Incoming update filter list for all interfaces is not set
Router ID 10.1.1.1
...