Cisco CCNP /  BSCI Exam Tutorial: 10 ISIS Details You Must Know!

Word Count:
268

Summary:
Chris Bryant, CCIE #12933, lists 10 ISIS details you must know in order to earn your CCNP.


Keywords:
ccnp, certification, cisco, isis, level, router, end, system, iis, hello, type, adjacency, level-1


Article Body:
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.

Best of luck on your CCNP exams!