How to Configure and Monitoring IS-IS on Junos Devices
IS-IS is a link-state interior gateway routing protocol. Like OSPF, IS-IS runs the Dijkstra shortest-path first (SPF) algorithm to create a database of the network’s topology and, from that database, to determine the best (that is, shortest) path to a destination.
The packets that IS-IS routers send to each other describing the network topology are called link-state protocol data units (link-state PDUs, or LSPs). In addition to describing the network topology that the router knows about, the link-state PDUs include IP routes, checksums, and other information.
To configure IS-IS on a router running the Junos operating system, you enable family iso processing on the interfaces on which you want IS-IS to run, and then you tell the router to form IS-IS adjacencies over that interface. Here’s how you do so for the ge-1/2/0.0 interface:
 user@junos-router# set interfaces ge-1/2/0 unit 0 family iso  user@junos-router# set protocols isis interface ge-1/2/0.0
Once you have completed the configuration of IS-IS, you can use these commands to monitor IS-IS routing on your network:
|show isis adjacency||Displays the router’s IS-IS neighbors.|
|show isis database||Displays entries in the IS-IS link-state database.|
|show isis interface||Displays the interfaces on which IS-IS is configured.|
|show isis route||Displays the contents of the IS-IS routing table.|
|show route protocol isis||Displays the routes learned by IS-IS.|