Configure the device level according to network planning
requirements:
- When the level of a device is Level-1, the device establishes
neighbor relationships with only Level-1 and Level-1-2 routers in
the same area and maintains only Level-1 LSDBs.
- When the level of a device is Level-2, the device can establish
neighbor relationship with Level-2 routers in the same area or different
areas and with Level-1-2 routers in different areas and maintain only
Level-2 LSDB.
- When the level of a device is Level-1-2, the
device can establish neighbor relationships with Level-1 and Level-2
routers and maintain Level-1 and Level-2 LSDBs.
If the levels of IS-IS devices are changed
during network operation, the IS-IS process will be restarted and
IS-IS neighbor relationships will be disconnected. Setting the levels
of devices when configuring IS-IS is recommended.