Configuring the IGP Shortcut

An IGP shortcut is configured on the ingress of a CR-LSP. The IGP shortcut prevents a route of a CR-LSP from being advertised to neighbors or used by the neighbors.

Context

IGP shortcut and forwarding adjacency cannot be configured simultaneously.

Procedure

Run system-view
The system view is displayed.
Run interface tunnel tunnel-number
The view of the MPLS TE tunnel interface is displayed.
Run mpls te igp shortcut [ isis | ospf ] or mpls te igp shortcut isis hold-time interval
The IGP shortcut is configured.

hold-time interval specifies the period after which IS-IS responds to the Down status of the TE tunnel.
If a TE tunnel goes Down and this parameter is not specified, IS-IS recalculates routes. If this parameter is specified, IS-IS responds to the Down status of the TE tunnel after only the specified interval elapses. It either recalculates routes or not depending on the TE tunnel status:
- If the TE tunnel goes Up, IS-IS does not recalculate routes.
- If the TE tunnel goes Down, IS-IS still recalculates routes.
Run mpls te igp metric { absolute | relative } value
The IGP metric of the TE tunnel is configured.

Either of the following parameters is set when configuring the metric value used by a TE tunnel during IGP shortcut path calculation:
- If absolute is configured, the TE tunnel metric value is equal to the configured metric value.
- If relative is configured, the TE tunnel metric value is equal to the sum of the IGP route metric value and relative TE tunnel metric value.
For IS-IS, run isis enable [ process-id ]
IS-IS is enabled on the tunnel interface.
For OSPF, run the following commands in sequence.
- Run ospf enable process-id area area-id
  OSPF is enabled on the tunnel interface.
  
  You can also run the network address wildcard-mask command in the OSPF view to enable network segment routing on the tunnel interface.
- Run quit
  
  The system view is displayed.
- Run ospf [ process-id ]
  
  The OSPF view is displayed.
- Run enable traffic-adjustment
  
  Traffic adjustment is enabled.
Run commit
The configuration is committed.

Follow-up Procedure

If a network fault occurs, IGP convergence is triggered. In this case, a transient forwarding status inconsistency may occur among nodes because of their different convergence rates, which poses the risk of microloops. To prevent microloops, perform the following steps:

Before you enable the OSPF TE tunnel anti-microloop function, configure CR-LSP backup parameters.

For IS-IS, run the following commands in sequence.
1. Run system-view
  
  The system view is displayed.
2. Run isis [ process-id ]
  
  An IS-IS process is created, and the IS-IS process view is displayed.
3. Run avoid-microloop te-tunnel
  
  The IS-IS TE tunnel anti-microloop function is enabled.
4. (Optional) Run avoid-microloop te-tunnel rib-update-delay rib-update-delay
  
  The delay in delivering the IS-IS routes whose outbound interface is a TE tunnel interface is set.
5. Run commit
  
  The configuration is committed.
For OSPF, run the following commands in sequence.
1. Run system-view
  
  The system view is displayed.
2. Run ospf [ process-id ]
  
  The OSPF view is displayed.
3. Run avoid-microloop te-tunnel
  
  The OSPF TE tunnel anti-microloop function is enabled.
4. (Optional) Run avoid-microloop te-tunnel rib-update-delay rib-update-delay
  
  The delay in delivering the OSPF routes whose outbound interface is a TE tunnel interface is set.
5. Run commit
  
  The configuration is committed.