To configure OSPF authentication, follow these steps:
1. Identify which type of authentication you want to use – either simple password or MD5 authentication.
2. Configure the authentication key to be used by OSPF.
3. Enable OSPF authentication on the routers that will be participating in OSPF.
Here are the detailed steps for each method:
Simple Password Authentication:
1. Identify the password to be used for authentication.
2. On each router, enter the following command: `router ospf [process ID] area [area ID] authentication [password]`. This will enable simple password authentication for OSPF.
MD5 Authentication:
1. Configure the authentication key on each router using the following command: `key chain [key name]`. Then, enter the following commands to create the key:
```
key [key-id]
key-string [key]
```
1. On each router, enter the following command: `router ospf [process ID] area [area ID] authentication message-digest`. This will enable MD5 authentication for OSPF.
2. Enter the following command on each router: `ip ospf message-digest-key [key-id] md5 [key]`. This configures OSPF to use the key for MD5 authentication.
Once authentication has been configured, OSPF will only form neighbors with other routers that have the same authentication settings.
