CLNS uses network service access points (NSAPs), similar to IP addresses found in IPv4, to identify end systems (hosts) and intermediate systems (routers). ES-IS enables the hosts and routers to discover each other. IS-IS is the interior gateway protocol (IGP) that carries ISO CLNS routes through a network.
Depending on your network topology, one or more of the following components are needed to route within a CLNS environment:
If a CLNS island does not contain any end systems, you do not need to configure ES-IS on a Services Router.
For more information about CLNS, see the ISO 8473 standards. For more information about IS-IS, see the ISO 10589 standard. For more information about ES-IS, see the ISO 9542 standard.