ISIS Configuration
Overview
Intermediate System to Intermediate System (IS-IS) is an interior routing protocol operating within a single administrative domain.It is a link-state routing protocol, operating by reliably flooding link state information throughout a network of routers. Each IS-IS router independently builds a database of the network's topology, aggregating the flooded network information. IS-IS uses Dijkstra's algorithm for computing the best path through the network. Packets (datagrams) are then forwarded, based on the computed ideal path, through the network to the destination.
Topology
Figure 4-4: ISIS Topology for VRF
Configuration IPv4 VRF
R1
#con t | Enter configuration mode. |
(config)#ip vrf vrf1 | Create vrf1 |
(config-vrf)#exit | Exit VRF mode |
(config)#router isis 1 vrf1 | Associate the ISIS process to vrf1 |
(config-router)#net 49.0001.0000.0000.0001.00 | Establish a network entity title for this instance, specifying the area address and the system ID. |
(config-router)#is-type level-1 | Configure instance 1 as level-1 routing |
(config-router)#exit | Exit router mode |
(config)#interface eth1 | Enter interface mode |
(config-if)#ip vrf forwarding vrf1 | Associate the interface to vrf1 |
(config-if)#ip address 2.2.2.1/24 | Configure the IP address 2.2.2.1 to eth1 |
(config-if)#ip router isis 1 | Enable ISIS routing on an instance for area 49 |
(config-if)#isis circuit-type level-1 | Configure interface as level-1 |
(config-if)#exit | Exit interface mode |
(config)#exit | Exit config mode |
R2
#con t | Enter configuration mode. |
(config)#ip vrf vrf1 | Create vrf1 |
(config-vrf)#exit | Exit VRF mode |
(config)#router isis 1 vrf1 | Associate the ISIS process to vrf1 |
(config-router)#net 49.0001.0000.0000.0002.00 | Establish a network entity title for this instance, specifying the area address and the system ID. |
(config-router)#is-type level-1 | Configure instance 1 as level-1 routing |
(config-router)#exit | Exit router mode |
(config)#interface eth1 | Enter interface mode |
(config-if)#ip vrf forwarding vrf1 | Associate the interface to vrf1 |
(config-if)#ip address 2.2.2.2/24 | Configure the IP address 2.2.2.1 to eth1 |
(config-if)#ip router isis 1 | Enable ISIS routing on an instance for area 49 |
(config-if)#isis circuit-type level-1 | Configure interface as level-1 |
(config-if)#exit | Exit interface mode |
(config)#exit | Exit config mode |
Validation
R1
#show clns neighbors
Tag 1: VRF : vrf1
System Id Interface SNPA State Holdtime Type Protocol
0000.0000.0002 eth1 5254.00d1.5789 Up 9 L1 IS-IS
R2
#show clns neighbors
Tag 1: VRF : vrf1
System Id Interface SNPA State Holdtime Type Protocol
0000.0000.0001 eth1 5254.0024.4323 Up 26 L1 IS-IS
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
Tag 1: VRF : vrf1
Destination Metric Next-Hop Interface Tag
C 2.2.2.0/24 10 -- eth1 0 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
Tag 1: VRF : vrf1
Destination Metric Next-Hop Interface Tag
C 2.2.2.0/24 10 -- eth1 0 0
Last modified date: 11-08-2023