FelicityHarwood917

To pass the BSCI exam and earn your CCNP, you've got to know ISIS inside and out. There are numerous similarities among ISIS and OSPF, but one main distinction is that ISIS has 3 diverse sorts of routers - Level 1 (L1), Level 2 (L2), and L1/L2.

L1 routers are contained in a single place, and are linked to other regions by an L1/L2 router. The L1 utilizes the L1/L2 router as a default gateway to reach destinations contained in other locations, much like an OSPF stub router makes use of the ABR as a default gateway.

L1 routers have no certain routing table entries regarding any destination outdoors their own place they will use an L1/L2 router as a default gateway to reach any external networks. ISIS L1 routers in the identical region should synchronize their databases with each and every other.

Just as we have L1 routers, we also have L2 routers. Anytime we're routing between areas (inter-region routing), an L2 or L1/L2 router should be involved. All L2 routers will have synchronized databases as properly.

Each L1 and L2 routers send out their own hellos. As with OSPF, hello packets permit ISIS routers to type adjacencies. The key 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 same 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 areas. 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 attainable for an L1 router to send data to one more location.

In the next portion of my ISIS tutorial, we'll take a far more detailed look at these ISIS hellos! ionways water ionizer microlite h2go