Huawei Quidway S6500 Series Operation Manual page 203

Operation Manual - Routing Protocol
Quidway S6500 Series Ethernet Switches
5.1.2 Two-level Structure of IS-IS Routing Protocol
ES
ES
ES
ES
IS
Figure 5-1 IS-IS topology
IS-IS adopts the two-level structure including Level-1 and Level-2 in a routing domain
(or the AS) to support the routing network at a large scale. A large RD is divided into
one or more areas. The Level-1 router manages the intra-area routing and is
responsible for communicating with other Level-1 routers in the same area. The
Level-2 router manages the inter-area routing. All of the Level-2 routers compose the
backbone network of the RD, which is responsible for the inter-area communications.
Every area has at least one router located on both the Level-1 and Level-2 (called
Level-1/Level-2 router), which connects the area to the backbone network. A
IS
IS
IS
IS
ES
Area 1
Routing Domain Boundary
IS-IS Area
End system
Intermediate system
Subnetwork Path
Interdomain Routing
Level 1 IS-IS Routing
Huawei Technologies Proprietary
Chapter 5 Integrated IS-IS Configuration
IS
Area 2
Routing Domain 1
Routing Domain 2
IS
ES
5-2
IS ES
IS
Area 3
IS
ES ES
Level 2 IS-IS Routing