Cisco CCNP and CCIE Study Notes

Consider two routers connected to each other via frame relay serial interfaces. The routers are able to ping each other but when IS-IS is configured on the routers, they fail to form neighbor adjacencies. Here is the config from the two routers

Router1

interface Serial2/0
 ip address 10.10.10.1 255.255.255.0
 ip router isis
 encapsulation frame-relay
 frame-relay map ip 10.10.10.1 102
 frame-relay interface-dlci 102
!
router isis
 net 49.0100.1111.1111.1111.00
 is-type level-1

Router2

interface Serial2/0
 ip address 10.10.10.2 255.255.255.0
 ip router isis
 encapsulation frame-relay
 frame-relay map ip 10.10.10.2 201
 frame-relay interface-dlci 201
!
router isis
 net 49.0100.2222.2222.2222.00
 is-type level-1

What needs to be done to get the two routers to see each other as IS-IS neighbors?

Note how the command to set the interface priority is ip ospf priority while for IS-IS it is just isis priority. (In the IS-IS case, the ip keyword is left out). An understanding of how IS-IS was originally an OSI routing protocol that was only later extended to IP leads one to appreciate the fact that the dropping of the ip keyword is more than just some inconsistent CLI developed by Cisco and is very likely a thought-out omission that makes perfect sense.