Configuring an IPv4 IS-IS Interface

IS-IS can send Hello packets through an interface to establish neighbor relationships and flood LSPs only after IS-IS is enabled on the interface.

Context

The level of an IS-IS device and level of an interface determine the level of a neighbor relationship. By default, Level-1 and Level-2 neighbor relationships will be established between two Level-1-2 devices. If only one level (Level-1 or Level-2) of neighbor relationships is required, you can configure the level of an interface to prevent the establishment of neighbor relationships of the other level.

After IS-IS is enabled on an interface, the interface will automatically send Hello packets, attempting to establish neighbor relationships. If a peer device is not an IS-IS device or if an interface is not expected to send Hello packets, suppress the interface. Then this interface only advertises routes of the network segment where the interface resides but does not send Hello packets. This suppression reduces the link bandwidth usage.

Procedure

Configure an IS-IS interface.
1. Run system-view
  The system view is displayed.
2. (Optional) Run isis interface limit disable
  The limit on the number of IS-IS interfaces that can be configured on the device is disabled.
  
  After this command is run, the number of IS-IS interfaces is no longer limited to the device threshold. To restore the limit on the device, run the undo isis interface limit disable command. If the number of IS-IS interfaces on the device is greater than or equal to the threshold before the configuration, no more IS-IS interfaces can be added on the device.
3. Run interface interface-type interface-number
  The interface view is displayed.
4. Run isis enable [ process-id ]
  An IS-IS interface is configured.
  
  After this command is run, the IS-IS device uses the specified interface to send Hello packets and flood LSPs.
  
  No neighbor relationship needs to be established between loopback interfaces. Therefore, if this command is run on a loopback interface, the routes of the network segment where the loopback interface resides will be advertised through other IS-IS interfaces.
5. Run commit
  The configuration is committed.
(Optional) Configure the level of an IS-IS interface.
1. Run isis circuit-level [ level-1 | level-1-2 | level-2 ]
  The level of the interface is configured.
  
  Changing the level of an IS-IS interface is valid only when the level of the IS-IS device is Level-1-2. If the level of the IS-IS device is not a Level-1-2, the level of the IS-IS device determines the level of the adjacency to be established.
2. Run commit
  The configuration is committed.
(Optional) Suppress an IS-IS interface.
1. Run isis silent [ advertise-zero-cost ]
  The IS-IS interface is suppressed.
  
  A suppressed IS-IS interface does not send or receive IS-IS packets. The routes of the network segment where the interface resides, however, can still be advertised to other devices within the area.
2. Run commit
  The configuration is committed.