Is-Is Area; Is-Is Network Types; Figure 10 Is-Is Area - Zte ZXR10 8900 Series User Manual

ZXR10 8900 Series User Manual (IPv4 Routing Volume)
F 10 IS-IS A
IGURE REA
36 Confidential and Proprietary Information of ZTE CORPORATION
IS-IS protocol also uses the Dijkstra SPF algorithm to calculate
routes. Based on the link state database, IS-IS protocol uses the
SPF algorithm to calculate the best route and then adds the route
to the IP routing table.

IS-IS Area

For convenience of link-state database management, concept of
IS-IS area is introduced. Routers in an area are only responsible
for maintaining the link state database in the local area to reduce
the traffic of the routers themselves.
IS-IS areas are classified into backbone areas and non-backbone
areas:
� Routers in the backbone area have the information about the
database of the entire network.
� Routers in a non-backbone area only have information about
the area.
Based on the area division, IS-IS defines three types of routers:
� L1 router exists in a non-backbone area and only exchanges
routing information with L1 router and L1/L2 router in the area.
� L2 router exists in the backbone area and exchanges routing
information with other L2 routers and L1/L2 routers.
� L1/L2 routers exist in a non-backbone area and exchanges
routing information between non-backbone area and the back-
bone area.
IS-IS area division and router types are shown in

IS-IS Network Types

There are two types of IS-IS networks:
Figure 10.