HassanSchramm314

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

L1 routers are contained in a single area, and are linked to other regions by an L1/L2 router. The L1 uses the L1/L2 router as a default gateway to reach destinations contained in other areas, significantly like an OSPF stub router uses the ABR as a default gateway.

L1 routers have no specific routing table entries relating to any destination outdoors their personal location they will use an L1/L2 router as a default gateway to reach any external networks. ISIS L1 routers in the very same location must synchronize their databases with every single other.

Just as we have L1 routers, we also have L2 routers. Anytime we're routing in between locations (inter-place routing), an L2 or L1/L2 router need to be involved. All L2 routers will have synchronized databases as effectively.

Each L1 and L2 routers send out their personal hellos. As with OSPF, hello packets enable ISIS routers to type adjacencies. The essential 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 same link, they will not form an adjacency.

An ISIS router can act as an L1 and an L2 router at the exact same time these routers are L1/L2 routers. An L1/L2 router can have neighbors in separate ISIS locations. The L1/L2 router will have two separate databases, though - one particular for L1 routes and one more for L2 routes. L1/L2 is the default setting for Cisco routers running ISIS. The L1/L2 router is the router that makes it possible for an L1 router to send data to yet another area.

In the next part of my ISIS tutorial, we'll take a more detailed look at these ISIS hellos! the best water ionizer oasis alkaline water scam