IS-IS Routing protocol configuration Step by Step [GNS3 Lab]
Before diving into configuration, you can refer to this article about IS-IS protocol basics:
Lab Topology
ISIS Configurations
R1 configuration:
R1(config)#int e1/0
R1(config-if)#ip address 172.31.10.1 255.255.255.252
R1(config-if)#no sh
*Jun 13 15:39:18.723: %LINK-3-UPDOWN: Interface Ethernet1/0, changed state to up
*Jun 13 15:39:19.723: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet1/0, changed state to up
R1(config-if)#exit
R1(config)#router isis
R1(config-router)#is-type level-1
R1(config-router)#net 11.1111.1111.1111.1111.00
R1(config-router)#exit
R1(config)#int e1/0
R1(config-if)#ip router isisR2 configuration:
R2(config)#int e1/0
R2(config-if)#ip address 172.31.10.2 255.255.255.252
R2(config-if)#no sh
R2(config)#int e1/1
R2(config-if)#ip address 172.31.0.1 255.255.255.252
R2(config-if)#no sh
R2(config)#router isis
R2(config-router)#net 11.1111.2222.2222.2222.00
R2(config-router)#is-type level-1-2
R2(config-router)#exit
R2(config)#int e1/0
R2(config-if)#ip router isis
R2(config)#int e1/1
R2(config-if)#ip router isisR3 configuration:
R3(config)#int e1/0
R3(config-if)#ip address 172.31.0.2 255.255.255.252
R3(config-if)#no sh
R3(config-if)#ip router isis
R3(config-if)#end
R3(config-if)#ip add
R3(config-if)#ip address 172.31.20.1 255.255.255.252
R3(config-if)#no sh
R3(config-if)#ip router isis
R3(config)#router isis
R3(config-router)#is-type level-1-2
R3(config-router)#net 22.2222.3333.3333.3333.00
R3(config-router)#exitR4 Configuration:
R4(config)#int e1/0
R4(config-if)#ip address 172.31.20.2 255.255.255.252
R4(config-if)#no sh
R4(config-if)#
*Jun 13 16:06:42.911: %LINK-3-UPDOWN: Interface Ethernet1/0, changed state to up
*Jun 13 16:06:43.911: %LINEPROTO-5-UPDOWN: Line protocol on Interface Ethernet1/0, changed state to up
R4(config-if)#exit
R4(config)#router isis
R4(config-router)#net 22.2222.4444.4444.4444.00
R4(config-router)#is-type level-1
R4(config-router)#exit
R4(config)#int e1/0
R4(config-if)#ip router isis
Verifications
* Verify ISIS neighbors on all devices:
R1#show isis neighbors
System Id Type Interface IP Address State Holdtime Circuit Id
R2 L1 Et1/0 172.31.10.2 UP 8 R2.01
----------------
R2#show isis neighbors
System Id Type Interface IP Address State Holdtime Circuit Id
R1 L1 Et1/0 172.31.10.1 UP 22 R2.01
R3 L2 Et1/1 172.31.0.2 UP 6 R3.01
---------------
R3#show isis neighbors
System Id Type Interface IP Address State Holdtime Circuit Id
R2 L2 Et1/0 172.31.0.1 UP 28 R3.01
R4 L1 Et1/1 172.31.20.2 UP 9 R4.01
---------------
R4#show isis neighbors
System Id Type Interface IP Address State Holdtime Circuit Id
R3 L1 Et1/0 172.31.20.1 UP 22 R4.01
- Verify ISIS CLNS neighbors:
R4#show clns neighbors
System Id Interface SNPA State Holdtime Type Protocol
R3 Et1/0 ca03.4068.001d Up 23 L1 IS-IS- Check routing tables:
R1:
R1#show ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
+ - replicated route, % - next hop override
Gateway of last resort is 172.31.10.2 to network 0.0.0.0
i*L1 0.0.0.0/0 [115/10] via 172.31.10.2, 00:22:13, Ethernet1/0
172.31.0.0/16 is variably subnetted, 3 subnets, 2 masks
i L1 172.31.0.0/30 [115/20] via 172.31.10.2, 00:22:21, Ethernet1/0
C 172.31.10.0/30 is directly connected, Ethernet1/0
L 172.31.10.1/32 is directly connected, Ethernet1/0
R2:
R2#show ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
+ - replicated route, % - next hop override
Gateway of last resort is not set
172.31.0.0/16 is variably subnetted, 5 subnets, 2 masks
C 172.31.0.0/30 is directly connected, Ethernet1/1
L 172.31.0.1/32 is directly connected, Ethernet1/1
C 172.31.10.0/30 is directly connected, Ethernet1/0
L 172.31.10.2/32 is directly connected, Ethernet1/0
i L2 172.31.20.0/30 [115/20] via 172.31.0.2, 00:18:11, Ethernet1/1
R3:
R3#show ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
+ - replicated route, % - next hop override
Gateway of last resort is not set
172.31.0.0/16 is variably subnetted, 5 subnets, 2 masks
C 172.31.0.0/30 is directly connected, Ethernet1/0
L 172.31.0.2/32 is directly connected, Ethernet1/0
i L2 172.31.10.0/30 [115/20] via 172.31.0.1, 00:24:18, Ethernet1/0
C 172.31.20.0/30 is directly connected, Ethernet1/1
L 172.31.20.1/32 is directly connected, Ethernet1/1
R4:
R4#show ip route
Codes: L - local, C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route, H - NHRP, l - LISP
+ - replicated route, % - next hop override
Gateway of last resort is 172.31.20.1 to network 0.0.0.0
i*L1 0.0.0.0/0 [115/10] via 172.31.20.1, 00:18:56, Ethernet1/0
172.31.0.0/16 is variably subnetted, 3 subnets, 2 masks
i L1 172.31.0.0/30 [115/20] via 172.31.20.1, 00:18:56, Ethernet1/0
C 172.31.20.0/30 is directly connected, Ethernet1/0
L 172.31.20.2/32 is directly connected, Ethernet1/0