This describes how to configure a virtual link. Through the configuration, you can establish a logical channel between non-adjacent areas to satisfy the requirements of OSPF for areas.
After area partition, the OSPF routes between non-backbone areas are updated with the help of the backbone area. OSPF stipulates that all the non-backbone areas should maintain the connectivity with the backbone area, and the backbone area should maintain its own connectivity.
However, in practical applications, the physical connectivity cannot be ensured due to the network topology restrictions. OSPF virtual link can be configured to solve this problem.
ospf [ process-id ]
area area-id
vlink-peer router-id [ dead dead-interval | hello hello-interval | retransmit retransmit-interval | smart-discover | trans-delay trans-delay-interval | [ 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 ] ] *
You must run this command at the peer end of the virtual link.
After virtual links are created, different default MTUs may be used on devices provided by different vendors. To ensure consistency, the MTU is set to 0 by default when the interface sends DD packets. For details, see Configuring the MTU in DD Packets.