Earning your CCNP certification and passing the BSCI exam depends on knowing the details of many Cisco technologies, ISIS chief among them. To help you prepare for exam success, here's a list of ISIS terminology and basic concepts that will help you pass this tough exam. Enjoy!

ISIS Terms:

Domain: section of the network under common administrative control

Area: logical segment of the network composed of contiguous routers and their data links

Intermediate System: A router.

End System: A host device.

The four levels of ISIS routing:

Level 0: ES-IS routing in the same subnet.

Level 1: IS-IS routing in the same area.

Level 2: IS-IS routing in the same domain.

Level 3: Inter-domain routing performed by InterDomain Routing Protocol (IDRP).

ISIS Adjacency Possibilities:

L1: Can form adjacency with any L1 in the same area and any L1/L2 in the same area.

L2: Can form adjacency with any L2 in any area, and with an L1/L2 in any area.

L1/L2: Can form adjacency with any L1 in the same area, L1/L2 in any area, and L2 in any area.

A router interfaces SNPA (Subnetwork Point Of Attachment) is its highest DLCI number if its on a Frame network, and its MAC address if the interface is on an Ethernet segment.

ISIS Hello Types:

ESH: ES Hello Sent by End Systems to discover a router.

ISH: IS Hello Send by Intermediate Systems to announce their presence. End Systems listen for these.

IIH: IS-to-IS Hello Send by one IS to be heard by another IS. These hellos makes IS-IS adjacencies possible.

Best of luck on your CCNP exams!