(Optional) Creating OSPF Virtual Links
Context
After OSPF areas are defined, OSPF route updates between non-backbone areas are transmitted through the backbone area. OSPF requires that all non-backbone areas maintain connectivity with the backbone area and that the backbone areas in different OSPF areas also maintain connectivity with each other. However, this is not true in some cases due to certain restrictions. To resolve this problem, you can configure OSPF virtual links.
Perform the following steps on a switch running OSPF.
Procedure
- Run system-view
The system view is displayed.
- Run ospf [ process-id ]
The OSPF process view is displayed.
- Run area area-id
The OSPF area view is displayed.
- Run vlink-peer router-id [ smart-discover | hello hello-interval | retransmit retransmit-interval | trans-delay trans-delay-interval | dead dead-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 ] ] *
A virtual link is created.
The vlink-peer (OSPF area) command must also be configured on the neighboring switch.
If plain is selected, the password is stored in plaintext in the configuration file. For security purposes, you are advised to select cipher so that the password is stored in ciphertext.
Simple authentication, MD5 authentication and HMAC-MD5 authentication have potential security risks. Therefore, HMAC-SHA256 authentication is recommended.
Only the S5720-EI, S5720-HI, S5730-HI, S5731-H, S5731-S, S5731S-H, S5731S-S, S5732-H, S6720-EI, S6720-HI, S6720S-EI, S6730-H, S6730S-H, S6730-S, and S6730S-S support the keychain keychain-name parameter.
Follow-up Procedure
Devices from different vendors may use different default MTUs. Therefore, after virtual links are created, the MTU needs to be set to the default value 0 for interfaces to send DD packets, which ensures the compatibility. For details, see Configuring an Interface to Fill in the DD Packet with the Actual MTU.