IOS Configuration: IS-IS
Basic Configuration
- Enable the routing process with
router isis - Configure the NET address (specifies router ID and area) with
net <NET> - Enable IS-IS per interface with
ip router isis
Basic configuration:
Router(config)# router isis
Router(config-router)# net 49.0001.0000.0000.0001.00
Router(config-if)# ip router isis
Optional Configuration
Changing the Router from Level 1-2
Cisco routers become level 1-2 routers by default.
A router can be configured to operate on only one level:
Router(config-router)# is-type {level-1 | level-2}
Routing level can alternatively be configured per interface:
Router(config-if)# isis circuit-type {level-1 | level-2-only}
Configuring Summarization
Summarization is configured on level 1-2 routers.
All level 1-2 routers in an area must summarize equivalently to avoid suboptimal routing.
Routes cannot be summarized within an area.
Router(config-router)# summary-address <network> <subnet>
Configuring NBMA
IS-IS only recognizes networks as either broadcast or point-to-point; if the interface is not a serial line to exactly one other endpoint, IS-IS assumes broadcast capability.
Point-to-point subinterfaces are recommended for IS-IS over NBMA.
Router(config)# interface s0
Router(config-if)# no ip address
Router(config-if)# encapsulation frame-relay
Router(config-if)# interface s0.1 point-to-point
Router(config-subif)# ip address 10.10.10.1 255.255.255.252
Router(config-subif)# ip router isis
Router(config-subif)# frame-relay dlci 629
Verification and Troubleshooting IS-IS Operation
show clns neighborshow clns interfaceshow isis database [detail]show isis spf-logdebug isis [adjacencies-packets | spf-statistics | update-packets]