Enable IS-IS on an Interface
This example shows the minimum configuration required for enabling IS-IS on an interface. R1 and R2 are two routers in the ABC instance connecting to the network 10.10.10.0/24. After enabling IS-IS on an interface, create a routing instance, and specify the Network Entity Title (NET). IS-IS explicitly specifies a NET to begin routing. NET is comprised of the area address and the system ID of the router.
Topology
Figure 13-101: Basic IS-IS Topology
Configuration
R1
#configure terminal | Enter configure mode. |
(config)#interface eth1 | Enter interface mode. |
(config)#ip address 21.21.21.2/24 | Configure IP address on interface. |
(config-if)#ip router isis ABC | Enable IS-IS routing on an interface for area 49 (ABC). |
(config-if)#exit | Exit interface mode. |
(config)#router isis ABC | Create an IS-IS routing instance for area 49 (ABC). |
(config-router)#is-type level-2-only | Configure instance as level-2-only routing. |
(config-router)#net 49.0000.0000.0001.00 | Set a Network Entity Title for this instance, specifying the area address and the system ID. |
(config-router)#commit | Commit candidate configuration to the running configuration |
R2
#configure terminal | Enter configure mode. |
(config)#interface eth1 | Enter interface mode. |
(config)#ip address 21.21.21.1/24 | Configure IP address on interface. |
(config-if)#ip router isis ABC | Enable IS-IS routing on an interface for area 49 (ABC). |
(config-if)#commit | Commit candidate configuration to the running configuration |
(config-if)#exit | Exit interface mode. |
(config)#router isis ABC | Create an IS-IS routing instance for area 49 (ABC). |
(config-router)#is-type level-2-only | Configure instance as level-2-only routing. |
(config-router)#net 49.0000.0000.0002.00 | Set a Network Entity Title for this instance, specifying the area address and the system ID. |
Validation
R1#show clns neighbors
Total number of L1 adjacencies: 0
Total number of L2 adjacencies: 1
Total number of adjacencies: 1
Tag ABC: VRF : default
System Id Interface SNPA State Holdtime Type Protocol
0000.0000.0002 eth1 5254.002a.230a Up 24 L2 IS-IS
R2#show clns neighbors
Total number of L1 adjacencies: 0
Total number of L2 adjacencies: 1
Total number of adjacencies: 1
Tag ABC: VRF : default
System Id Interface SNPA State Holdtime Type Protocol
0000.0000.0001 eth1 5254.00dc.0b76 Up 6 L2 IS-IS
R1#show clns is-neighbors
Tag ABC: VRF : default
System Id Interface State Type Priority Circuit Id
0000.0000.0002 eth1 Up L2 64 0000.0000.0001.01
R2#show clns is-neighbors
Tag ABC: VRF : default
System Id Interface State Type Priority Circuit Id
0000.0000.0001 eth1 Up L2 64 0000.0000.0001.01
R1#show isis interface
eth1 is up, line protocol is up
Routing Protocol: IS-IS (ABC)
Network Type: Broadcast
Circuit Type: level-1-2
Local circuit ID: 0x01
Extended Local circuit ID: 0x00000003
Local SNPA: 5254.00dc.0b76
IP interface address:
21.21.21.2/24
IPv6 interface address:
fe80::5054:ff:fedc:b76/64
Level-2 Metric: 10/10, Priority: 64, Circuit ID: 0000.0000.0001.01
Number of active level-2 adjacencies: 1
Level-2 LSP MTU: 1492
Next IS-IS LAN Level-2 Hello in 0 milliseconds
R2#show isis interface
eth1 is up, line protocol is up
Routing Protocol: IS-IS (ABC)
Network Type: Broadcast
Circuit Type: level-1-2
Local circuit ID: 0x01
Extended Local circuit ID: 0x00000003
Local SNPA: 5254.002a.230a
IP interface address:
21.21.21.1/24
IPv6 interface address:
fe80::5054:ff:fe2a:230a/64
Level-2 Metric: 10/10, Priority: 64, Circuit ID: 0000.0000.0001.01
Number of active level-2 adjacencies: 1
Level-2 LSP MTU: 1492
Next IS-IS LAN Level-2 Hello in 1 seconds
R1#show ip isis route
Codes: C - connected, E - external, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, D - discard, e - external metric
** - invalid
Tag ABC: VRF : default
Destination Metric Next-Hop Interface Tag
C 21.21.21.0/24 10 -- eth1 0
R2#show ip isis route
Codes: C - connected, E - external, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, D - discard, e - external metric
** - invalid
Tag ABC: VRF : default
Destination Metric Next-Hop Interface Tag
C 21.21.21.0/24 10 -- eth1 0
R1#show isis topology
Tag ABC: VRF : default
IS-IS paths to level-2 routers
System Id Metric Next-Hop Interface SNPA
0000.0000.0001 --
0000.0000.0002 10 0000.0000.0002 eth1 5254.002a.230a
R2#show isis topology
Tag ABC: VRF : default
IS-IS paths to level-2 routers
System Id Metric Next-Hop Interface SNPA
0000.0000.0001 10 0000.0000.0001 eth1 5254.00dc.0b76
0000.0000.0002 --
R1#show isis database
Tag ABC: VRF : default
IS-IS Level-2 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime ATT/P/OL
0000.0000.0001.00-00* 0x00000009 0x6C2D 980 0/0/0
0000.0000.0001.01-00* 0x00000003 0x1DBB 980 0/0/0
0000.0000.0002.00-00 0x0000000A 0x5444 980 0/0/0
R2#show isis database
Tag ABC: VRF : default
IS-IS Level-2 Link State Database:
LSPID LSP Seq Num LSP Checksum LSP Holdtime ATT/P/OL
0000.0000.0001.00-00 0x00000009 0x6C2D 942 0/0/0
0000.0000.0001.01-00 0x00000003 0x1DBB 942 0/0/0
0000.0000.0002.00-00* 0x0000000A 0x5444 944 0/0/0
Last modified date: 10/16/2023