How to configure ISIS on Cisco IOS-XR

Here is a quick example of configuring ISIS between two cisco IOS-XR devices. The configuration is a little different than how we do on Cisco IOS or IOS-XE devices, however, theoretically, it is exactly the same so it doesn’t take much to understand and learn the configuration. So let’s quickly jump to the configuration.

Configuration Task:

Configure IOS-XR routers XR-1 and XR-3 for ISIS IPv4 and IPv6 point-point adjacencies.Topology is given below…

Configurations:

XR-1 Config :

interface Loopback1
 ipv4 address 5.5.5.5 255.255.255.255
 ipv6 address 2222::7/128
!
interface GigabitEthernet0/0/0/1
 ipv4 address 20.20.20.1 255.255.255.252
 ipv6 address 2007::1/126
!
router isis CORE
 is-type level-1
 net 49.0000.0000.0005.00
 address-family ipv4 unicast
 !
 address-family ipv6 unicast
  single-topology
 !
 interface Loopback1
  address-family ipv4 unicast
  !
  address-family ipv6 unicast
  !
 !
 interface GigabitEthernet0/0/0/1
  circuit-type level-1
  point-to-point
  address-family ipv4 unicast
  !
  address-family ipv6 unicast
  !       
 !





XR-3 Config:


interface Loopback1
 ipv4 address 6.6.6.6 255.255.255.252
 ipv6 address 2222::8/128
!
interface GigabitEthernet0/0/0/0
 ipv4 address 20.20.20.2 255.255.255.252
 ipv6 address 2007::2/126
 ipv6 enable
!
router isis CORE
 net 49.0000.0000.0008.00
 address-family ipv4 unicast
 !
 address-family ipv6 unicast
  single-topology
 !
 interface Loopback1
  address-family ipv4 unicast
  !
  address-family ipv6 unicast
  !
 !
 interface GigabitEthernet0/0/0/0
  circuit-type level-1
  point-to-point
  address-family ipv4 unicast
  !
  address-family ipv6 unicast
  !
 !

Verification:

XR-1:


RP/0/0/CPU0:ios#sh isis  neighbors 
Wed May 26 01:41:30.352 UTC

IS-IS CORE neighbors:
System Id      Interface        SNPA           State Holdtime Type IETF-NSF
R1             Gi0/0/0/0        *PtoP*         Up    25       L1   Capable 
0000.0000.0008 Gi0/0/0/1        *PtoP*         Up    23       L1   Capable 


RP/0/0/CPU0:ios#sh route ipv4 isis 
Wed May 26 01:41:57.720 UTC

i L1 1.1.1.1/32 [115/20] via 10.10.10.5, 00:50:21, GigabitEthernet0/0/0/0
i L1 6.6.6.4/30 [115/20] via 20.20.20.2, 00:50:20, GigabitEthernet0/0/0/1
i L1 10.10.10.0/30 [115/20] via 10.10.10.5, 00:50:21, GigabitEthernet0/0/0/0
i L1 20.20.20.4/30 [115/20] via 20.20.20.2, 00:50:20, GigabitEthernet0/0/0/1
RP/0/0/CPU0:ios#sh route ipv6 isis 
Wed May 26 01:42:02.670 UTC

i L1 2001::/126 
      [115/20] via fe80::e83:95ff:fe99:1f01, 00:50:26, GigabitEthernet0/0/0/0
i L1 2008::/126 
      [115/20] via fe80::e83:95ff:fe35:a501, 00:50:25, GigabitEthernet0/0/0/1
i L1 2222::1/128 
      [115/20] via fe80::e83:95ff:fe99:1f01, 00:50:26, GigabitEthernet0/0/0/0
i L1 2222::8/128 
      [115/20] via fe80::e83:95ff:fe35:a501, 00:50:24, GigabitEthernet0/0/0/1
RP/0/0/CPU0:ios#




XR-2:

RP/0/0/CPU0:ios#sh isis neighbors 
Wed May 26 01:49:22.680 UTC

IS-IS CORE neighbors:
System Id      Interface        SNPA           State Holdtime Type IETF-NSF
0000.0000.0005 Gi0/0/0/0        *PtoP*         Up    29       L1   Capable 

Total neighbor count: 1

RP/0/0/CPU0:ios#sh route ipv4 isis 
Wed May 26 01:50:15.776 UTC

i L1 1.1.1.1/32 [115/30] via 20.20.20.1, 00:58:36, GigabitEthernet0/0/0/0
i L1 5.5.5.5/32 [115/20] via 20.20.20.1, 00:58:37, GigabitEthernet0/0/0/0
i L1 10.10.10.0/30 [115/30] via 20.20.20.1, 00:58:36, GigabitEthernet0/0/0/0
i L1 10.10.10.4/30 [115/20] via 20.20.20.1, 00:58:37, GigabitEthernet0/0/0/0
RP/0/0/CPU0:ios#sh route ipv6 isis 
Wed May 26 01:50:19.936 UTC

i L1 2001::/126 
      [115/30] via fe80::e83:95ff:fe05:b102, 00:58:40, GigabitEthernet0/0/0/0
i L1 2002::/126 
      [115/20] via fe80::e83:95ff:fe05:b102, 00:58:41, GigabitEthernet0/0/0/0
i L1 2222::1/128 
      [115/30] via fe80::e83:95ff:fe05:b102, 00:58:40, GigabitEthernet0/0/0/0
i L1 2222::7/128 
      [115/20] via fe80::e83:95ff:fe05:b102, 00:58:41, GigabitEthernet0/0/0/0
RP/0/0/CPU0:ios#

Conclusion:

Above is the small snippet of isis config on the ios-xr devices, I am going to expand this to frr and lfa etc in my future blog posts. The overall config is very simple and seamless. Thanks for reading. Happy learning.

Also I have a youtube video created on this blog, please visit if you want to see the live configuration.

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