Configuring an IPv6 IS-IS Interface to Automatically Adjust the Link Cost

Configuring an IPv6 IS-IS interface to automatically adjust the link cost based on link quality facilitates route selection control and improves network reliability.

Context

A bit error refers to the deviation between a bit that is sent and the bit that is received. The bit error rate (BER) refers to the number of bit errors divided by the total number of bits transferred during a studied time interval. During data transmission, a high BER may degrade or even interrupt services.

To prevent this problem, configure IPv6 IS-IS interfaces to automatically adjust link costs based on link quality so that unreliable links are not used by the optimal routes.

Procedure

Perform the following steps for a conventional IS-IS process:
1. Run system-view
  The system view is displayed.
2. Run isis [ process-id ]
  The IS-IS view is displayed.
3. Run ipv6 enable topology ipv6
  IPv6 is enabled for the IS-IS process.
4. Run quit
  Return to the system view.
5. Run interface interface-type interface-number
  The interface view is displayed.
6. Run ipv6 enable
  IPv6 is enabled on the interface.
7. Run isis ipv6 enable [ process-id ]
  IPv6 IS-IS is enabled on the interface, and the specified process ID is associated with the interface.
8. Run isis ipv6 link-quality low incr-cost { cost-value | max-reachable }
  The IPv6 IS-IS interface is enabled to automatically adjust the link cost based on link quality.
  The cost parameter specifies the link cost adjustment value. After this parameter is specified:
  If the link quality changes from good to low, the link cost equals the original link cost plus the adjustment value. If the new link cost exceeds the maximum link cost allowed, the maximum link cost allowed applies:
  The maximum link cost is 63, if the cost style is narrow, narrow-compatible, or compatible.
  The maximum link cost is 16777214, if the cost style is wide or wide-compatible.
  
  If the link quality changes from low to good, the original link cost applies.
9. Run commit
  The configuration is committed.
Perform the following steps for an IS-IS multi-instance process:
1. Run system-view
  The system view is displayed.
2. Run isis [ process-id ]
  The IS-IS view is displayed.
3. Run ipv6 enable topology ipv6
  IPv6 is enabled for the IS-IS process.
4. Run multi-instance enable iid iid-value
  The conventional IS-IS process is configured as an IS-IS multi-instance process.
5. Run quit
  Return to the system view.
6. Run interface interface-type interface-number
  The interface view is displayed.
7. Run ipv6 enable
  IPv6 is enabled on the interface.
8. Run isis ipv6 enable [ process-id ]
  IPv6 IS-IS is enabled on the interface, and the specified process ID is associated with the interface.
9. Run isis [ process-id process-id ] ipv6 link-quality low incr-cost { cost-value | max-reachable }
  The IPv6 IS-IS interface is enabled to automatically adjust the link cost based on link quality.
  The cost parameter specifies the link cost adjustment value. After this parameter is specified:
  If the link quality changes from good to low, the link cost equals the original link cost plus the adjustment value. If the new link cost exceeds the maximum link cost allowed, the maximum link cost allowed applies:
  The maximum link cost is 63, if the cost style is narrow, narrow-compatible, or compatible.
  The maximum link cost is 16777214, if the cost style is wide or wide-compatible.
  
  If the link quality changes from low to good, the original link cost applies.
10. Run commit
  The configuration is committed.