Failed to Establish IS-IS Neighbor Relationships

Procedure

1. Check whether devices on both ends of the link have the matching IS-IS levels.
   • Run the display current-configuration configuration isis | include is-level command to check the level configurations of IS-IS processes on both ends.
   • Run the display current-configuration interface interface-type interface-number | include isis circuit-level command to check the IS-IS level configuration of the specified interface.

   IS-IS neighbor relationship can be established when IS-IS interfaces on both ends of the link have the matching IS-IS levels.

   

   If you cannot view the IS-IS level of an interface using the display current-configuration interface interface-type interface-number | include isis circuit-level command, the interface uses the default IS-IS level. To view the default IS-IS level, run the display default-parameter isis command to check the Circuit-Level field.

   Requirements on the IS-IS levels of interfaces on both ends of a link are as follows:

   • If the IS-IS level of the local interface is Level-1, the IS-IS level of the remote interface must be Level-1 or Level-1-2.

   • If the IS-IS level of the local interface is Level-2, the IS-IS level of the remote interface must be Level-2 or Level-1-2.

   • If the IS-IS level of the local interface is Level-1-2, the IS-IS level of the remote interface can be Level-1, Level-2, or Level-1-2.

   If the IS-IS levels of interfaces on both ends of a link do not match, perform either of the following operations to change the IS-IS level:

   • Run the is-level command in the IS-IS view to change the global IS-IS level.
   • Run the isis circuit-level command in the interface view to change the interface IS-IS level.

2. Check whether devices on both ends of the link have the matching area addresses.

   Run the display current-configuration configuration isis command to check area address information.

   

   If IS-IS Level-1 neighbor relationship needs to be established between devices on both ends, ensure that the two devices reside in the same area.

   A maximum of three area addresses can be configured for an IS-IS process. Devices on both ends can establish IS-IS Level-1 neighbor relationship when the two devices have a same area address.

   When IS-IS Level-2 neighbor relationship needs to be established between the two devices, the two devices can have the same or different area addresses.

   If the area addresses of the two devices are different, run the network-entity command in the IS-IS view to set the same area address for the two devices.

3. Check whether devices on both ends of the link have the authentication mode.

   Run the display current-configuration interface interface-type interface-number | include isis authentication-mode command to check the IS-IS authentication modes of the interfaces on both ends of the link.

   If the two interfaces use different authentication modes, run the isis authentication-mode command in the view of one interface to ensure that this interface has the same authentication mode and password as the other interface.