Concept Guide

Command History
Version Description
9.9(0.0) Introduced on the FN IOM.
9.2(0.0) Introduced on the MXL 10/40GbE Switch IO Module.
Usage Information
Congure a network entity title (the net command) to specify the area address and the router system ID.
To establish adjacencies and establish dynamic routing, enable routing on one or more interfaces.
You can congure only one IS-IS routing process to perform Level 2 routing. A level-1-2 designation performs
Level 1 and Level 2 routing at the same time.
Related Commands
• net — congures an IS-IS network entity title (NET) for the routing process.
• is-type — assigns a type for a given area.
isis circuit-type
Congure the adjacency type on interfaces.
Syntax
isis circuit-type {level-1 | level-1-2 | level-2-only}
To return to the default values, use the no isis circuit-type command.
Parameters
level-1 You can form a Level 1 adjacency if there is at least one common area address between
this system and neighbors. You cannot form Level 2 adjacencies on this interface.
level-1-2 You can form a Level 1 and Level 2 adjacencies when the neighbor is also congured as
Level-1-2 and there is at least one common area, if not, a Level 2 adjacency is established.
This setting is the default.
level-2-only You can form a Level 2 adjacencies when other Level 2 or Level 1-2 routers and their
interfaces are congured for Level 1-2 or Level 2. Level 1 adjacencies cannot be
established on this interface.
Defaults level-1-2
Command Modes INTERFACE
Supported Modes Full–Switch
Command History
Version Description
9.9(0.0) Introduced on the FN IOM.
9.2(0.0) Introduced on the MXL 10/40GbE Switch IO Module.
Usage Information
Because the default establishes Level 1 and Level 2 adjacencies, you do not need to congure this command.
Routers in an IS-IS system must be congured as a Level 1-only, Level 1-2, or Level 2-only system.
Only congure interfaces as Level 1 or Level 2 on routers that are between areas (for example, a Level 1-2 router)
to prevent the software from sending unused hello packets and wasting bandwidth.
Intermediate System to Intermediate System (IS-IS) 785