IS-IS route Induction Technology

IS-ISThat is, from the intermediate system to the intermediate systemRoutingSelectProtocolIs a routing protocol proposed by ISO. IS-IS a link status protocol. In this protocol, the IS router IS responsible for exchanging Routing Information Based on Link overhead and determining the network topology. IS-IS similar to the Open Shortest Path (OSPF) protocol for TCP/IP networks.

Due to the unlimited number of theoretically hops, the routing protocol for link status is used for routing implementation in a large autonomous system. Therefore, there is a need for hierarchical Topology Design to achieve smaller topology tables and route tables, reduce LSA or LSP flooding, and prevent frequent SPF computing.

The IS-IS routing protocol has some problems in routing induction on cisco routers. Let's discuss it now.

For example, four detailed routes are

 
 

  
  
172.16.4.0 255.255.255.0  
  
  
 
  
  
172.16.5.0 255.255.255.0  
  
  
 
  
  
172.16.6.0 255.255.255.0  
  
  
 
  
  
172.16.7.0 255.255.255.0 
 
 

According to our calculation, the generated network number should be

 
 

  
  
172.16.4.0 255.255.252.0 
 
 

Based on relevant information, the following commands are required to complete route induction:

 
 

  
  
router(config)#router isis  
  
  
 
  
  
router(config-router)#summary-address 172.16.4.0 255.255.252.0 ？  
  
  
 
  
  
level-1 Summarize into level-1 area  
  
  
 
  
  
level-1-2 Summarize into both area and sub-domain  
  
  
 
  
  
level-2 Summarize into level-2 sub-domain 
 
 

If the parameter is not followed, level-2 induction is used by default. This is what we want to see.

In contrast to the OSPF routing protocol, in order to implement route induction between regions, you only need to implement the induction command on the ABR, And the configuration on other routers is actually invalid ).

IS-IS routing protocol. On a cisco router, the default L1/2 role IS used only for the VBR connected to other regions in one region, if there is only one vrol1 with the L1/2 Role in the region, but there are other vrouters with the L1/2 role, the Operation will fail. All routers with L1/2 roles must be summarized to succeed. In addition, L1 routers do not need to be configured, and it does not work even if it is configured on L1 routers.