(Optional) Creating OSPF Virtual Links

This section describes how to create logical links between backbone areas and to ensure the OSPF network connectivity.

Context

After OSPF is divided into different areas, OSPF routes between non-backbone areas are updated through route exchanges within the backbone area. Therefore, OSPF requires that all non-backbone areas keep connected to the backbone area and devices within the backbone area also keep connected. In real-world scenarios, however, these requirements cannot be met due to various limitations. Configuring OSPF virtual links can solve the problem.

Procedure

Run system-view
The system view is displayed.
Run ospf [ process-id ]
The OSPF process is started and OSPF view is displayed.
Run area area-id
The OSPF area view is displayed.
Run vlink-peer router-id [ dead dead-interval | hello hello-interval | retransmit retransmit-interval | trans-delay trans-delay-interval | smart-discover | [ simple [ plain plain-text | [ cipher ] cipher-text ] | { md5 | hmac-md5 | hmac-sha256 } [ key-id { plain plain-text | [ cipher ] cipher-text } ] | authentication-null | keychain keychain-name ] ] ^*
A virtual link is created.

The virtual link must also be configured on the neighboring router.
The default value is recommended when a virtual link is created. You can modify the value as required. Suggestions for configuring parameters are as follows:
- The smaller the hello value, the faster the router detects network topology changes, and the more network resources are consumed.
- If the retransmit value is set too small, LSAs may be retransmitted. Setting the parameter to a large value is recommended on a low-speed network.
- The authentication modes of a virtual link and the backbone area must be the same.
Run commit
The configuration is committed.