3Com Switch 7750 Configuration Guide Guide

IS-IS Basic Configuration 323
Configuring Default
Route Generation
In an IS-IS routing domain, a Level-1 router maintains the LSDB for the local area
only and generates the routes within the local area only. A Level-2 router
maintains the LSDB for the backbone within the IS-IS routing domain and
generates the routes for the backbone only. To transfer packets to another area, a
Level-1 router in an area needs to first transfer the packets to the nearest Level-1-2
router within the local area. This requires the default route at Level-1.
Configuring Protocol
Priority
For a router running multiple routing protocols, routing information needs to be
shared and selected by the routing protocols. The system assigns a priority for
each routing protocol. When multiple routing protocols discover a route to the
same destination, the protocol with the highest priority will dominate.
Configuring a Cost Style In IS-IS routing protocol, routing cost of a link can be expressed in one of the
following two modes:
■ Narrow: In this mode, routing cost ranges from 1 to 63.
■ Wide: In this mode, routing cost ranges from 1 to 2
24
-1, namely, 1 to
16777215.
You can specify to support either mode or both.
Table 245 Configure route summarization
Operation Command Description
Enter system view system-view -
Enter IS-IS view isis [ tag ] Required
Configure route
summarization
summary ip-address ip-mask
[ level-1 | level-1-2 | level-2 ]
Optional
By default, the system
performs no route
summarization.
Table 246 Configure default route generation
Operation Command Description
Enter system view system-view -
Enter IS-IS view isis [ tag ] Required
Configure default route
generation
default-route-advertise [
route-policy
route-policy-name ]
Optional
The default route is advertised
to only the routers at the
same level.
Table 247 Configure protocol priority
Operation Command Description
Enter system view system-view -
Enter IS-IS view isis [ tag ] Required
Configure protocol priority
preference [ value | clns | ip ]
value
Optional
The default priority of IS-IS
routes is 15.