Configuring OSPF authentication on a virtual link

Set the OSPF virtual-link authentication type that will be used for authentication with the remote ABR when the command is used in the vlink context.

OSPF supports the same methods of authentication for virtual links as it does for interfaces in an area. In the default configuration, OSPF authentication is disabled. Only one method of authentication can be active on a virtual link at a time. If one method is configured on a virtual link, configuring the alternative method on the same link automatically replaces the first method. Both ends of a virtual link must use the same authentication method and related credentials.

Prerequisites

You must be in the router vlink configuration context, as indicated by the switch(config-router-vlink)# prompt.

Procedure

Set the OSPF virtual-link authentication type using the following command. For command details, see authentication.
authentication {message-digest | simple-text | null}

For example, the following command sets virtual-link authentication type to simple-text.
```
switch(config-router-vlink)# authentication simple-text
```
For simple-text authentication, set the password using the following command. For command details, see authentication-key.
authentication-key <password>
For example:
```
switch(config-router-vlink)# authentication-key secure
```
For MD5 authentication, set the password using the following command. For command details, see message-digest-key md5.
message-digest-key md5 <key>
For example:
```
switch(config-router-vlink)# message-digest-key md5 100
```