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JUNOS Cookbook by Aviva Garrett

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11.2. Viewing the IS-IS Link-State Database

Problem

You want to look at each router's link-state database to make sure that all the IS-IS routers know about each other.

Solution

Use the show isis database command to view the contents of the link-state database:

	aviva@RouterG> show isis database
	 
IS-IS level 1 link-state database:
	LSP ID                      Sequence Checksum Lifetime Attributes
	RouterG.00-00                   0x65   0xfa35      851 L1 L2 Attached
	RouterA.00-00                   0x5e   0xf289      661 L1 L2

	RouterA.02-00                   0x59   0xeda9      632 L1 L2
	  3 LSPs
	IS-IS level 2 link-state database:
	LSP ID                      Sequence Checksum Lifetime Attributes
	RouterH.00-00                   0x61   0xa315      923 L1 L2
	RouterG.00-00                   0x61   0x125e      741 L1 L2
	RouterG.02-00                   0x5e   0x79f0      741 L1 L2
	  3 LSPs

Discussion

IS-IS routers exchange LSPs that describe each individual router's view of the network topology and they store the LSPs in a link-state database. The SPF algorithm then runs on the link-state database to create the IS-IS routing table. Use the show isis database command to look at the contents of the link-state database. In this recipe, RouterG is a Level 1–Level 2 router, so you see two link-state databases, one for each level.

The first part of the output shows that the Level 1 link-state database has three LSPs. The entry for RouterG includes the attach bit (Attached), which indicates that it is connected to another IS-IS area. From the configuration, you know that this router is connected to area 30.

If you check on the other Level 2 router, its Level 2 database is identical to that of ...

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