10 ISIS Details You Must Know!

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, heres 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.

Best of luck on your CCNP exams!

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Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage (www.thebryantadvantage.com), home of FREE CCNA and CCNP tutorials and daily exam questions, as well as The Ultimate CCNA and CCNP Study Packages.

For a FREE copy of his latest e-books, “How To Pass The CCNA” or “How To Pass The CCNP”, and for free daily exam question, visit the website and download your copies!