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Cisco CCNP / BSCI Exam Tutorial: ISIS Router Sorts

To pass the BSCI exam and earn your CCNP, you have got to know ISIS inside and out. There are several similarities in between ISIS and OSPF, but one particular key difference is that ISIS has 3 distinct types of routers - Level 1 (L1), Level 2 (L2), and L1/L2. water ionizer .

L1 routers are contained in a single region, and are connected to other locations by an L1/L2 router. The L1 utilizes the L1/L2 router as a default gateway to reach destinations contained in other regions, a lot like an OSPF stub router uses the ABR as a default gateway.

L1 routers have no certain routing table entries concerning any destination outside their own region they will use an L1/L2 router as a default gateway to reach any external networks. ISIS L1 routers in the identical area must synchronize their databases with every single other.

Just as we have L1 routers, we also have L2 routers. Anytime we're routing amongst locations (inter-area routing), an L2 or L1/L2 router need to be involved. All L2 routers will have synchronized databases as nicely. tour vitamin c shower filter .


Both L1 and L2 routers send out their personal hellos. As with OSPF, hello packets enable ISIS routers to form adjacencies. The important difference right here is that L1 routers send out L1 hellos, and L2 routers send out L2 hellos. If you have an L1 router and an L2 router on the identical link, they will not type an adjacency.

An ISIS router can act as an L1 and an L2 router at the identical time these routers are L1/L2 routers. An L1/L2 router can have neighbors in separate ISIS regions. The L1/L2 router will have two separate databases, though - 1 for L1 routes and one more for L2 routes. L1/L2 is the default setting for Cisco routers operating ISIS. The L1/L2 router is the router that tends to make it achievable for an L1 router to send data to an additional location. portable water ionizer .

In the subsequent component of my ISIS tutorial, we'll take a more comprehensive appear at these ISIS hellos!