> For the complete documentation index, see [llms.txt](https://paul-gleason.gitbook.io/cisco-ios-cheat-sheet/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://paul-gleason.gitbook.io/cisco-ios-cheat-sheet/subsection/ospf.md).

# OSPF

### Base Setup

```
enable
config t
interface {interface} {interface_#}
no shutdown
ip address {ip_address} {subnet}
router ospf 1
network {network_address} {wildcard} area {area_#}
```

Example

```
enable
config t
interface GigabitEthernet 0/0
no shutdown
ip address 10.8.1.1 255.255.255.248
router ospf 1
network 10.8.1.0 0.0.0.7 area 0
```

### Add Authentication 

#### MD5:

[Documentation](https://networklessons.com/ospf/how-to-configure-ospf-md5-authentication)

```
enable 
config t 
interface {interface} {interface #} 
ip ospf message-digest-key {instance #} md5 {password}
ip ospf authentication message-digest
```

Example:

```
enable 
config t 
interface GigabitEthernet 0/0 
ip ospf message-digest-key 1 md5 testing 
ip ospf authentication message-digest
```

Verification:

```
enable
show ip ospf interface fastEthernet 0/0
```

Output:

<figure><img src="/files/ZYkpHznNt7R4a2fAcvpV" alt=""><figcaption><p>Verification Output</p></figcaption></figure>

#### SHA-512:

[Documentation](https://networklessons.com/cisco/ccie-routing-switching-written/ospf-hmac-sha-extended-authentication)

```
enable
config t
key chain {key_name}
key {#}
cryptographic-algorithm {algorithm}
key-string {password}
exit
interface {interface} {interface_#}
ip ospf authentication key-chain {key_name}
```

Example:

```
enable
config t
key chain R2
key 1
cryptographic-algorithm hmac-sha-512
key-string testing
exit
interface GigabitEthernet 0/1
ip ospf authentication key-chain R2
```

Verification:

```
enable
show ip ospf interface GigabitEthernet 0/1 | begin auth
```

Output:

<figure><img src="/files/heHoCXoFG6bpFpvsMRah" alt=""><figcaption><p>Verification Output</p></figcaption></figure>