When IS-IS is enabled, the default level-capability is level 1/2. This means that the router operates with both level 1 and level 2 routing. To change the default value in order for the router to operate as a level 1 router or a level 2 router, you must explicitly modify the level value.
If the level is modified, the protocol shuts down and restarts. Doing this can affect adjacencies and routes.
The level-capability value can be configured on the global level and also on the interface level. The level-capability value determines which level values can be assigned on the router level or on an interface-basis.
In order for the router to operate as a level 1 only router or as a level 2 only router, you must explicitly specify the level-number value.
Select level-1 to route only within an area.
Select level-2 to route to destinations outside an area, toward other eligible level 2 routers.
To configure the router level, enter the following commands:
config>router# isis
level-capability {level-1|level-2|level-1/2}
level {1|2}Example
config>router# isis
config>router>isis# level-capability 1/2
config>router>isis# level 2The following example displays the configuration:
A:ALA-A>config>router>isis# info
#------------------------------------------
echo "ISIS"
#------------------------------------------
level-capability level-1/2
level 2
----------------------------------------------
A:ALA-A>config>router>isis#