Configuring Auto Routes

Context

After you configure auto routes, TE tunnels act as logical links to participate in IGP route calculation and tunnel interfaces are used as the outbound interfaces of packets. Devices on network nodes determine whether to advertise LSP information to neighboring nodes to instruct packet forwarding. Two modes are available for auto routes:

Configuring IGP shortcut: A device uses a TE tunnel for local route calculation and does not advertise the TE tunnel to its peers as a route. Therefore, the peers of this device cannot use the TE tunnel for route calculation.
Configuring forwarding adjacency: A device uses a TE tunnel for local route calculation and advertises the TE tunnel to its peers as a route. Therefore, the peers of this device can use the TE tunnel for route calculation.

Perform the following configurations on the ingress node of an MPLS TE tunnel.

IGP shortcut and forwarding adjacency are exclusive to each other.
When using forwarding adjacency to advertise LSP information to other nodes for bidirectional detection on links, you must configure another tunnel for transmitting packets in the opposite direction, and then enable forwarding adjacency on the two tunnels.

Procedure

Configuring IGP Shortcut
1. Run system-view
  The system view is displayed.
2. Run interface tunnel interface-number
  The interface view of the MPLS TE tunnel is displayed.
3. Run mpls te igp shortcut [ isis | ospf ]
  The IGP shortcut is configured.
  
  By default, the IGP shortcut is not configured. If the IGP type is not specified when the IGP shortcut is configured, both IS-IS and OSPF are supported by default.
4. Run mpls te igp metric { absolute absolute-value | relative relative-value }
  The IGP metric value for the tunnel is configured.
  
  By default, the metric value used by the TE tunnel is the same as that of the IGP.
  You can specify a metric value used by the TE tunnel when path is calculated in the IGP shortcut feature.
  - If the absolute metric is used, the TE tunnel is equal to the configured metric value.
  - If the relative metric is used, the TE tunnel is equal to the sum of the metric value of the corresponding IGP path and relative metric value.
5. Run mpls te commit
  The current TE tunnel configuration is committed.
6. You can select either of the following modes to configure IGP shortcut.
  - For IS-IS, run isis enable [ process-id ]
    
    IS-IS is enabled on the tunnel interface.
  - For OSPF, run the following commands in sequence:
    1. Run the quit command to return to the system view.
    2. Run the ospf [ process-id ] command to enter the OSPF view.
    3. Run the enable traffic-adjustment command to enable IGP shortcut function.
Configuring Forwarding Adjacency
1. Run system-view
  The system view is displayed.
2. Run interface tunnel interface-number
  The tunnel interface view is displayed.
3. Run mpls te igp advertise [ hold-time interval ]
  The forwarding adjacency is enabled.
4. Run mpls te igp metric { absolute absolute-value | relative relative-value }
  The IGP metric value for the tunnel is configured.
  
  The IGP metric value must be set properly to ensure that LSP information is advertised and used correctly. For example, the metric of a TE tunnel must be less than that of IGP routes to ensure that the TE tunnel is used as a route link.
  
  If relative is configured and IS-IS is used as an IGP, this step cannot modify the IS-IS metric value. To change the IS-IS metric value, configure absolute in this step.
5. Run mpls te commit
  The current tunnel configuration is committed.
6. You can select either of the following modes to enable the forwarding adjacency.
  - For IS-IS, run isis enable [ process-id ]
    
    IS-IS is enabled on the tunnel interface.
  - For OSPF, run the following commands in sequence:
    1. Run the ospf enable [ process-id ] area area-id command to enable the OSPF process on the tunnel interface.
      Alternatively, run the network address wildcard-mask command in the OSPF area view to advertise routes destined for the network segment to which the tunnel interface belongs in the OSPF area.
    2. Run quit
      
      The system view is displayed.
    3. Run ospf [ process-id ]
      
      The OSPF view is displayed.
    4. Run enable traffic-adjustment advertise
      
      Forwarding adjacency is enabled.