IS-IS neighbor establishment fails.
Symptom:
When the link is normal, IS-IS neighbor establishment fails.
Operation steps
1. Check whether the IS-IS Levels of the devices at both ends of the link match. Run
the display current-configuration configuration isis | include is-level command to view the Level configuration of the IS-IS processes at both ends.
Run the display current-configuration interface interface-type interface-number | include isis circuit-level command to view the IS-IS Level configuration of the interface.
It is necessary to ensure that the levels at both ends of the link match to establish an IS-IS neighbor.
Note: If you cannot query the interface Level using the display current-configuration interface interface-type interface-number | include isis circuit-level command, it means that the interface level is the default value. For this default value, you can use the display default-parameter isis command to view the Circuit-Level field.
The principle of interface level matching is as follows:
If the level of the local interface is Level-1, the level of the peer interface must be Level-1 or Level-1-2.
If the local interface Level is Level-2, the peer interface Level must be Level-2 or Level-1-2.
If the local interface Level is Level-1-2, the peer interface Level can be Level-1, Level-2, or Level-1-2.
If the Levels at both ends of the link do not match, run the following command to modify the Level:
Run the is-level command in the IS-IS view to modify the global IS-IS Level of the device.
Run the isis circuit-level command in the interface view to modify the IS-IS Level of the device interface.
2. Check whether the regional addresses of the devices at both ends of the link match.
Run the display current-configuration configuration isis command to view the regional address information of the devices.
Note: If Level-1 neighbors are established at both ends of the link, you need to ensure that the devices at both ends of the link are in the same area.
An IS-IS process can be configured with up to three area addresses. As long as one area address is the same at both ends, a Level-1 neighbor can be established.
When establishing an IS-IS Level-2 neighbor, it is not necessary to determine whether the area addresses match.
If the two ends of the link do not have the same area address, use the network-entity command in IS-IS view to modify the area address of the device.
3. Check whether the authentication modes of the devices at both ends of the link match.
Run the display current-configuration interface interface-type interface-number | include isis authentication-mode command to check the IS-IS authentication configuration of the interfaces at both ends.
If the authentication modes at both ends do not match, run the isis authentication-mode command in the IS-IS interface view at both ends of the link to set the same authentication type and the same authentication password at both ends of the link.
The device cannot learn IS-IS routes.
Symptom:
When the link is normal, the device cannot learn IS-IS routes.
Operation steps
1. Check whether the IS-IS neighbor is established normally.
Run display isis peer on each device on the path to check whether the IS-IS neighbor is established normally.
If the IS-IS neighbor relationship fails, see IS-IS neighbor establishment fails.
2. Check whether the IS-IS routing table is correct.
Run the display isis route command to view the IS-IS routing table.
If the specified route exists in the IS-IS routing table, run the display ip routing-table ip-address [ mask | mask-length ] verbose command to check whether there is a route with a higher protocol priority than IS-IS in the IP routing table.
Note: If the State field is Active Adv, it means that the route is an active route. If there are routes with multiple protocols with the same prefix, the route with a higher protocol priority is preferred as the active route.
If there are routes with a higher protocol priority than IS-IS in the IP routing table, adjust the configuration according to the actual network plan.
3. Check whether the IS-IS cost type matches.
Run the display current-configuration configuration isis command on the device that advertises routes and the device that cannot learn routes to check the IS-IS cost type configuration.
Only routes with the same cost type can be learned.
IS-IS overhead types can be configured in the following five modes:
narrow : Receive and send packets whose overhead value type is narrow.
narrow-compatible : Can receive packets with overhead value types of narrow and wide, but only sends narrow packets.
compatible : Can receive or send packets with cost value types of narrow and wide.
wide-compatible : Can receive packets with cost value types of narrow and wide, but only sends wide packets.
wide : Receive or send packets with an overhead value type of wide.
If one end is configured as narrow and the other end is configured as wide or wide-compatible, the two ends cannot communicate with each other.
If one end is configured as narrow-compatible and the other end is configured as wide, the two ends cannot communicate with each other.
If the IS-IS cost types of the devices at both ends of the link do not match, run the cost-style command to modify the configuration.