The IS-IS host name mapping mechanism maps host names to system IDs for IS-IS devices, including dynamic host name mapping and static host name mapping. Dynamic host name mapping takes precedence over static host name mapping. When both a dynamic host name and a static host name are configured, the dynamic host name takes effect.
On an IS-IS router where host name exchange is disabled, information about IS-IS neighbors and LSDBs shows that each device in an IS-IS routing domain is identified by a system ID with 12-digit hexadecimal number, for example, aaaa.eeee.1234. This device identification method is complex and not easy to use. The host name exchange mechanism facilitates IS-IS network management and maintenance.
When an IS-IS neighbor is displayed, the system ID of the IS-IS neighbor is replaced by its host name. When the neighbor is the DIS, the system ID of the DIS is also replaced by its host name.
When an LSP in the IS-IS LSDB is displayed, the system ID in the LSP ID is replaced by the host name of the IS-IS device that advertises the LSP.
When details about the IS-IS LSDB are displayed, the Host Name field is added to the LSP generated by the device where dynamic host name exchange is enabled, and the system ID in the Host Name field is replaced by the dynamic host name of the device that generates the LSP.
On a device where dynamic host name mapping is enabled, dynamic host name information is advertised as TLV 137 (Dynamic Hostname TLV) in LSPs. When you run IS-IS commands on other devices to view IS-IS information, the system ID of the local device is replaced by the configured host name. The host name is easier to identify and memorize than the system ID.
The Dynamic Hostname TLV is optional and can be inserted anywhere in an LSP. The value of this TLV cannot be empty. A device can determine whether to send LSPs carrying TLV 137, while the device that receives LSPs can determine whether to ignore TLV 137 or whether to obtain TLV 137 for its mapping table.
Static host name mapping allows you to configure the mapping between host names and system IDs of other IS-IS devices on a device. Static host name mapping takes effect only on the local device and is not advertised using LSPs.