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 interface’s SNPA (Subnetwork Point Of Attachment) is its highest DLCI number if it’s 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.

Here's to your CCNP exam success!

Chris Bryant
CCIE #12933
www.thebryantadvantage.com