## Configuring OSPF Static Neighbors
Open Shortest Path First (OSPF) is a popular link-state routing protocol used in IP networks. While OSPF typically discovers neighbors dynamically, there may be situations where static neighbors are preferable, such as in environments with specific routing requirements or when controlling neighbor relationships. This tutorial will guide you through the steps to configure OSPF static neighbors, providing terminal examples for clarity.
### Prerequisites
1. **Basic OSPF Configuration**: Ensure that OSPF is configured on your router.
2. **Connectivity**: Ensure there is IP connectivity between the routers you want to configure as static neighbors.
### Step 1: Basic OSPF Configuration
First, configure OSPF on both routers with their respective interfaces and OSPF process.
#### Router A Configuration
```plaintext
RouterA# configure terminal
RouterA(config)# router ospf 1
RouterA(config-router)# network 192.168.1.0 0.0.0.255 area 0
RouterA(config-router)# exit
RouterA(config)# interface GigabitEthernet 0/0
RouterA(config-if)# ip address 192.168.1.1 255.255.255.0
RouterA(config-if)# no shutdown
RouterA(config-if)# exit
RouterA# exit
```
#### Router B Configuration
```plaintext
RouterB# configure terminal
RouterB(config)# router ospf 1
RouterB(config-router)# network 192.168.1.0 0.0.0.255 area 0
RouterB(config-router)# exit
RouterB(config)# interface GigabitEthernet 0/0
RouterB(config-if)# ip address 192.168.1.2 255.255.255.0
RouterB(config-if)# no shutdown
RouterB(config-if)# exit
RouterB# exit
```
### Step 2: Configuring OSPF Static Neighbors
After the basic OSPF configuration is complete, you can specify static OSPF neighbors. This can be done within the OSPF routing process.
#### Router A Configuration
On Router A, configure Router B as a static neighbor:
```plaintext
RouterA# configure terminal
RouterA(config)# router ospf 1
RouterA(config-router)# neighbor 192.168.1.2
RouterA(config-router)# exit
RouterA# exit
```
#### Router B Configuration
On Router B, configure Router A as a static neighbor:
```plaintext
RouterB# configure terminal
RouterB(config)# router ospf 1
RouterB(config-router)# neighbor 192.168.1.1
RouterB(config-router)# exit
RouterB# exit
```
### Step 3: Verifying OSPF Neighbors
After configuring the static neighbors, verify that OSPF has established the neighbor relationship.
#### On Router A
```plaintext
RouterA# show ip ospf neighbor
```
You should see an output indicating Router B as a neighbor:
```plaintext
Neighbor ID Pri State Dead Time Address Interface
192.168.1.2 1 FULL/BDR 00:00:37 192.168.1.2 GigabitEthernet0/0
```
#### On Router B
```plaintext
RouterB# show ip ospf neighbor
```
The output should indicate Router A as a neighbor:
```plaintext
Neighbor ID Pri State Dead Time Address Interface
192.168.1.1 1 FULL/BDR 00:00:38 192.168.1.1 GigabitEthernet0/0
```
### Step 4: Testing Connectivity
It’s crucial to ensure that the routers can ping each other to confirm connectivity.
#### On Router A
```plaintext
RouterA# ping 192.168.1.2
```
#### On Router B
```plaintext
RouterB# ping 192.168.1.1
```
If the pings are successful, the static OSPF neighbor configuration is complete.
### Step 5: Troubleshooting OSPF Static Neighbors
If the OSPF neighbors do not come up as expected, consider the following troubleshooting steps:
1. **Check OSPF Configuration**:
- Ensure the OSPF process ID is the same on both routers.
- Verify that the network statements cover the correct interfaces.
2. **Verify IP Connectivity**:
- Ensure both routers can ping each other.
3. **Check OSPF Status**:
- Use `show ip ospf neighbor` to check the neighbor status.
- Use `show ip ospf` to verify OSPF parameters.
4. **Interface Status**:
- Ensure the interfaces are up and not administratively down. Check with `show ip interface brief`.
5. **Firewall/Access Control**:
- Ensure there are no firewalls or ACLs blocking OSPF packets (multicast address 224.0.0.5).
### Conclusion
Configuring OSPF static neighbors can enhance control over neighbor relationships, particularly in specific network designs. This tutorial has provided a step-by-step guide, including terminal commands and verification methods. By following these steps, you can successfully implement static OSPF neighbors in your network environment.
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