Enabling IS-IS for Interfaces of Different Network Types

An interface can send Hello packets to establish neighbor relationships and floods LSPs only after you enable IS-IS on it. You can configure different IS-IS attributes for interfaces of different network types.

Context

The methods to establish IS-IS neighbor relationships on a broadcast network and a P2P network are different. Therefore, you need to set different IS-IS attributes for interfaces of different types:

On a broadcast network, IS-IS needs to select the designated intermediate system (DIS). You can set the DIS priority for IS-IS interfaces to enable the device with the highest DIS priority to be elected as the DIS.

On a P2P network, IS-IS does not need to select the DIS. Therefore, the DIS priority does not need to be configured for interfaces. To ensure P2P link reliability, configure IS-IS to establish a neighbor relationship on two P2P interfaces in 3-way mode for unidirectional link fault detection.

Procedure

Establish an IS-IS neighbor relationship on a broadcast link.
1. Access the system view.
  system-view
2. Access the interface view.
  interface interface-type interface-number
3. Enable IS-IS on the interface.
  isis enable [ process-id ]
  
  After this command is run, IS-IS establishes neighbor relationships and floods LSPs through this interface.
  
  Loopback interfaces are not used to establish neighbor relationships. If IS-IS is enabled on a loopback interface, IS-IS advertises the routes of the network segment where the interface resides through other IS-IS interfaces.
4. Configure the level of the interface.
  isis circuit-level [ level-1 | level-1-2 | level-2 ]
  
  By default, the level of an interface is level-1-2.
  
  When two Level-1-2 devices establish IS-IS neighbor relationship, they establish both Level-1 and Level-2 neighbor relationships. To allow the two Level-1-2 devices to establish only Level-1 or Level-2 neighbor relationship, change the level of interfaces.
  
  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 device is not Level-1-2, the level of the device determines the level of the established neighbor relationship.
5. Set a DIS priority for the interface.
  isis dis-priority priority [ level-1 | level-2 ]
  
  A larger value indicates a higher priority.
  
  By default, the DIS priority of Level-1 and Level-2 broadcast interfaces is 64.
6. Suppress the interface.
  isis silent [ advertise-zero-cost ]
  
  By default, an IS-IS interface is not suppressed.
  
  When an IS-IS interface is suppressed, the interface no longer sends or receives IS-IS packets. The routes of the network segment where the interface resides, however, can still be advertised to other IS-IS devices within the same AS.
7. Configure a delay for the IS-IS neighbor relationship establishment.
  isis delay-peer track last-peer-expired[ delay-time delay-interval ]
  
  By default, delay-interval is 60s.
  
  If a new delay-interval is configured and it is less than the remaining time of the ongoing delay, the new delay-interval takes effect immediately; if the new delay-interval is greater than the remaining time of the ongoing delay, the ongoing delay continues until the new delay-interval takes effect at the next delay.
Establish an IS-IS neighbor relationship on a P2P link.
1. Access the system view.
  system-view
2. Access the interface view.
  interface interface-type interface-number
3. Enable IS-IS on the interface.
  isis enable [ process-id ]
4. Configure the level of the interface.
  isis circuit-level [ level-1 | level-1-2 | level-2 ]
  
  By default, the level of an interface is level-1-2.
5. Set the network type of the interface to P2P.
  isis circuit-type p2p
  
  By default, the network type of an interface is determined by the physical type of the interface.
  
  When the network type of an IS-IS interface changes, the interface configuration changes accordingly:
  - After a broadcast interface is simulated as a P2P interface using the isis circuit-type p2p command, the interval for sending Hello packets, number of Hello packets that IS-IS does not receive from a neighbor before the neighbor is declared Down, interval for retransmitting LSPs on a P2P link, and various IS-IS authentication modes are restored to the default settings; other configurations such as the DIS priority, DIS name, and interval for sending CSNPs on a broadcast network become invalid.
  - After the undo isis circuit-type command is run to restore the default network type of an IS-IS interface, the interval for sending Hello packets, number of Hello packets that IS-IS does not receive from a neighbor before the neighbor is declared Down, interval for retransmitting LSPs on a P2P link, various IS-IS authentication modes, DIS priority, and interval for sending CSNPs on a broadcast network are restored to the default settings.
6. Set a negotiation mode for the interface.
  isis ppp-negotiation { 2-way | 3-way [ only ] }
  
  By default, the negotiation mode is 3-way.
7. Configure IS-IS not to check the IP addresses of received Hello packets.
  isis peer-ip-ignore
  
  By default, IS-IS checks the IP addresses of received Hello packets.
8. Configure SICP negotiation status check on the interface.
  isis ppp-osicp-check
  
  By default, the OSICP negotiation status of a PPP interface does not affect the status of an IS-IS interface.
  
  This command applies only to PPP interfaces and is invalid for other P2P interfaces.
  
  After this command is run, the OSICP negotiation status of a PPP interface affects the status of an IS-IS interface. When PPP detects that the OSI network fails, the link status of the IS-IS interface goes Down and the routes of the network segment where the interface resides are not advertised through LSPs.
9. (Optional) Configure a delay for the IS-IS neighbor relationship establishment.
  isis delay-peer track last-peer-expired [ delay-time delay-interval ]
  
  By default, delay-interval is 60s.
  
  If a new delay-interval is configured and it is less than the remaining time of the ongoing delay, the new delay-interval takes effect immediately; if the new delay-interval is greater than the remaining time of the ongoing delay, the ongoing delay continues until the new delay-interval takes effect at the next delay.