Editing IS-IS (section)

== Hostname resolution ==
Let's imagine, that engineer examines L2 or L1 database, or needs to view a specific LSP. Each LSP has LSP ID, consisting of System ID, Pseudonode ID and Fragment ID. Because generally System ID is router's loopback address, remembering which loopback address to which router is not always convenient.

Similar problem is observed in OSPF, when LSDB or specific LSA is checked - they are listed by Advertising router, which is actually an IP. In case of OSPF, in order to overcome difficulty of remembering router IPs or consulting with list, local DNS resolution can be configured. But as it might be understood, this is not very convenient and fast way, especially during troubleshooting ongoing issues.

IS-IS solves this problem in a very elegant manner - in each LSP there is '''TLV 137''', which displays hostname of the originating router. By this means, all routers know hostnames of other routers in the level by examining LSPs. That's why when viewing LSP in L2 or L1 database, they are displayed by hostname, not System ID.

On the other hand, if needed, hostnames and their matching System IDs can be easily seen from IS-IS which keeps their list.