AubryPeel770

To pass the BSCI exam and earn your CCNP, you have got to know ISIS inside and out. There are a lot of similarities between ISIS and OSPF, but one key distinction is that ISIS has 3 distinct sorts of routers - Level 1 (L1), Level 2 (L2), and L1/L2. L1 routers are contained in a single area, and are connected to other areas 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 makes use of the ABR as a default gateway. L1 routers have no certain routing table entries with regards to any destination outside their own location they will use an L1/L2 router as a default gateway to reach any external networks. ISIS L1 routers in the exact same region 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 places (inter-location 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 allow ISIS routers to type adjacencies. The important difference 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 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, although - a single for L1 routes and yet another for L2 routes. L1/L2 is the default setting for Cisco routers running ISIS. The L1/L2 router is the router that makes it achievable for an L1 router to send data to another area. team In the next part of my ISIS tutorial, we'll take a a lot more detailed appear at these ISIS hellos!