WickmanFoshee344

WickmanFoshee344 — Mon, 27 Aug 2012 06:49:09 GMT

WickmanFoshee344: Created page with 'To pass the BSCI exam and earn your CCNP, you've got to know ISIS inside and out. There are numerous similarities between ISIS and OSPF, but a single key difference is that ISIS…'

To pass the BSCI exam and earn your CCNP, you've got to know ISIS inside and out. There are numerous similarities between ISIS and OSPF, but a single key difference is that ISIS has three distinct kinds 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 makes use of the L1/L2 router as a default gateway to reach destinations contained in other places, a lot like an OSPF stub router makes use of the ABR as a default gateway.

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

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

Both L1 and L2 routers send out their personal hellos. As with OSPF, hello packets allow ISIS routers to type adjacencies. The important distinction 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 regions. The L1/L2 router will have two separate databases, though - a single 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 achievable for an L1 router to send data to yet another region.

In the next part of my ISIS tutorial, we'll take a more comprehensive look at those ISIS hellos! [http://www.youtube.com/watch?v=Z8LhAu1rBU8 ionways athena] [http://www.youtube.com/watch?v=DGnMPgS0vLA official link] [http://www.ionizeroasis.com/jupiter-athena-water-ionizer.html athena water discussions]

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