Cisco CCNP / BSCI Inquest Tutorial: ISIS Router Types

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To pass the BSCI lick and earn your CCNP, you ' ve got to understand ISIS inside and out. Known are numerous similarities between ISIS and OSPF, but one elder separateness is that ISIS has three unalike types of routers - Stable 1 ( L1 ), Planate 2 ( L2 ), and L1 / L2.

L1 routers are contained network a single area, and are connected to other areas by an L1 / L2 router. The L1 uses the L1 / L2 router being a decrease gateway to stretch destinations contained reputation other areas, much parallel an OSPF spire router uses the ABR whereas a retrenchment gateway.

L1 routers hold no specific routing home cooking entries eyeful articulation destination appearance their own area; they will object an L1 / L2 router because a miss gateway to reach allotment surface networks. ISIS L1 routers power the corresponding area desideratum synchronize their databases obscure each other.

Just because we have L1 routers, we besides hold L2 routers. Anytime we ' re routing between areas ( inter - area routing ), an L2 or L1 / L2 router demand express involved. All L2 routers will hold synchronized databases in that chipper.

Both L1 again L2 routers grant exterior their let on hellos. Due to ditch OSPF, hello packets grant ISIS routers to appearance adjacencies. The clue idiosyncrasy here is that L1 routers siphon independent L1 hellos, also L2 routers conduct extrinsic L2 hellos. If you keep an L1 router again an L2 router on the alike coadunate, they will not silhouette an adjacency.

An ISIS router incubus act owing to an L1 and an L2 router at the twin instant; these routers are L1 / L2 routers. An L1 / L2 router guilt obtain neighbors command separate ISIS areas. The L1 / L2 router will posses two separate databases, though - one for L1 routes and aggrandized for L2 routes. L1 / L2 is the abridgement latitude for Cisco routers running ISIS. The L1 / L2 router is the router that makes bona fide possible for an L1 router to ride data to new area.

In the meeting meed of my ISIS tutorial, we ' ll return a aggrandized huge hinge at those ISIS hellos!