Reference Guide

836 | Intermediate System to Intermediate System (IS-IS)
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Usage
Information
You must configure a network entity title (the net command) to specify the area address and the router
system ID.
You must enable routing on one or more interfaces to establish adjacencies and establish dynamic
routing.
Only one IS-IS routing process can be configured to perform Level 2 routing. A level-1-2 designation
performs Level 1 and Level 2 routing at the same time.
Related
Commands
isis circuit-type
e
Configure the adjacency type on interfaces.
Syntax
isis circuit-type {level-1 | level-1-2 | level-2-only}
To return to the default values, enter no isis circuit-type.
Parameters
Defaults
level-1-2
Command Modes
INTERFACE
Usage
Information
Because the default establishes Level 1 and Level 2 adjacencies, you do not need to configure this
command. Routers in an IS-IS system should be configured as a Level 1-only, Level 1-2, or Level
2-only system.
Only configure 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.
isis csnp-interval
e
Configure the IS-IS complete sequence number PDU (CSNP) interval on an interface.
Syntax
isis csnp-interval seconds [level-1 | level-2]
To return to the default values, enter the no isis csnp-interval [seconds] [level-1 | level-2]
command.
net Configure an IS-IS network entity title (NET) for a routing process.
is-type Assign a type for a given area.
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 configured as
Level-1-2 and there is at least one common area, if not, then a Level 2 adjacency is
established.
This 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 configured for Level 1-2 or Level 2. Level 1 adjacencies cannot be
established on this interface.