Intermediate systems and end systems

IS-IS uses the following categories to describe devices within an IS-IS routing domain (similar to an OSPF Autonomous System):

• Intermediate System (IS) - A device capable of forwarding packets from one device to another within the domain. In Internet Protocol (IP) terminology, an IS is a router.
• End System (ES) - A device capable of generating or receiving packets within the domain. In IP terminology, an ES is an end node or IP host.

When you configure IS-IS on a device, the device is an IS.

An IS-IS network contains Intermediate Systems (ISs) and host systems shows an example of an IS-IS network.

An IS-IS network contains Intermediate Systems (ISs) and host systems

Note

Since the implementation of IS-IS does not route OSI traffic but instead routes IP traffic, IP hosts are shown instead of ESs.

The other basic IS-IS concepts illustrated in this figure are explained in the following sections.