Configuration Example of Interaction Between IS-IS and BGP

Owned by Tracy Yang
Nov 18, 2024
4 min read

Networking Requirements

Figure 1. Configuration Example of Interaction Between IS-IS and BGP

Config Example of Interaction Between IS-IS and BGP.jpg

As shown in Figure 1, there are three switches (Switch A, Switch B and Switch C) in this sample network. IS-IS routing protocol runs between Switch A and Switch B, and EBGP routing protocol runs between Switch B and Switch C. To enable communication between Switch A and Switch C, you need to configure to redistribute IS-IS routes to BGP routes, and BGP routes to IS-IS routes on Switch B.

Follow the configuration roadmap below to complete the configuration:

  1. Configure VLAN interface and IP address for each interface to make the network reachable.

  2. Enable IS-IS on Switch A and Switch B, and enable EBGP on Switch B and Switch C.

  3. On Switch B, configure route redistribution between route protocol IS-IS and BGP.

Procedure

Switch A

Step1         Configure VLAN interface.

admin@SwitchA# set vlans vlan-id 100 l3-interface vlan100 admin@SwitchA# set vlans vlan-id 1000 l3-interface vlan1000 admin@SwitchA# set interface gigabit-ethernet te-1/1/3 family ethernet-switching native-vlan-id 100 admin@SwitchA# set interface gigabit-ethernet te-1/1/1 family ethernet-switching native-vlan-id 1000 admin@SwitchA# set l3-interface vlan-interface vlan100 address 192.168.20.1 prefix-length 24 admin@SwitchA# set l3-interface vlan-interface vlan1000 address 192.168.1.6 prefix-length 24

Step2       Enable IS-IS for the network segment.

admin@SwitchA# set protocols isis area-tag instance1 network-entity 32.0001.0040.0220.0001.00 admin@SwitchA# set protocols isis area-tag instance1 interface vlan100 ipv4-routing admin@SwitchA# set protocols isis area-tag instance1 interface vlan1000 ipv4-routing

 Step3       Enable IP routing.

admin@SwitchA# set ip routing enable true

 Step4       Commit the configuration.

admin@SwitchA# commit

Switch B

 Step1        Configure VLAN interface.

admin@SwitchB# set vlans vlan-id 1000 l3-interface vlan1000 admin@SwitchB# set vlans vlan-id 33 l3-interface vlan33 admin@SwitchB# set interface gigabit-ethernet te-1/1/1 family ethernet-switching native-vlan-id 1000 admin@SwitchB# set interface gigabit-ethernet te-1/1/5 family ethernet-switching native-vlan-id 33 admin@SwitchB# set l3-interface vlan-interface vlan1000 address 192.168.1.2 prefix-length 24 admin@SwitchB# set l3-interface vlan-interface vlan33 address 33.33.33.130 prefix-length 24

 Step2       Enable IS-IS for the specified network segment.

admin@SwitchB# set protocols isis area-tag instance1 network-entity 32.0001.0040.0220.0002.00 admin@SwitchB# set protocols isis area-tag instance1 interface vlan33 ipv4-routing admin@SwitchB# set protocols isis area-tag instance1 interface vlan1000 ipv4-routing

 Step3       Configure EBGP connection between Switch B and Switch C.

admin@SwitchB# set protocols bgp local-as 200 admin@SwitchB# set protocols bgp router-id 2.2.2.2 admin@SwitchB# set protocols bgp ebgp-requires-policy false admin@SwitchB# set protocols bgp ipv4-unicast network 192.168.1.0/24 admin@SwitchB# set protocols bgp neighbor 33.33.33.33 remote-as 100

 Step4       Enable IP routing.

admin@SwitchB# set ip routing enable true

 Step5       Commit the configuration.

admin@SwitchB# commit

Switch C

 Step1        Configure VLAN interface.

admin@SwitchC# set vlans vlan-id 33 l3-interface vlan33 admin@SwitchC# set vlans vlan-id 2000 l3-interface vlan2000 admin@SwitchC# set interface gigabit-ethernet te-1/1/3 family ethernet-switching native-vlan-id 33 admin@SwitchC# set interface gigabit-ethernet te-1/1/1 family ethernet-switching native-vlan-id 2000 admin@SwitchC# set l3-interface vlan-interface vlan33 address 33.33.33.33 prefix-length 24 admin@SwitchC# set l3-interface vlan-interface vlan2000 address 55.55.55.55 prefix-length 24

 Step2       Configure EBGP connection between Switch B and Switch C.

admin@SwitchC# set protocols bgp local-as 100 admin@SwitchC# set protocols bgp router-id 3.3.3.3 admin@SwitchC# set protocols bgp ebgp-requires-policy false admin@SwitchC# set protocols bgp ipv4-unicast network 55.55.55.0/24 admin@SwitchC# set protocols bgp neighbor 33.33.33.130 remote-as 200

 Step3       Enable IP routing.

admin@SwitchC# set ip routing enable true

 Step4       Commit the configuration.

admin@SwitchC# commit

View IS-IS Route Table on Switch A

  • On Switch A, use command run show isis route to check IS-IS route table, the route 55.55.55.0/24 does not exist.

admin@SwitchA# run show isis route Area instance1: IS-IS L1 IPv4 routing table: Prefix Metric Interface Nexthop Label(s) ---------------------------------------------------------- 33.33.33.0/24 20 vlan1000 192.168.1.2 - 192.168.1.0/24 20 vlan1000 192.168.1.2 - IS-IS L2 IPv4 routing table: Prefix Metric Interface Nexthop Label(s) ---------------------------------------------------------- 33.33.33.0/24 20 vlan1000 192.168.1.2 - 192.168.1.0/24 20 vlan1000 192.168.1.2 -

Configuring Switch B to Import Route between BGP and IS-IS

admin@SwitchB# set protocols isis area-tag instance1 redistribute ipv4-routing bgp level-1 admin@SwitchB# set protocols isis area-tag instance1 redistribute ipv4-routing bgp level-2 admin@SwitchB# set protocols bgp ipv4-unicast redistribute isis admin@SwitchB# commit

View IS-IS Route Table on Switch A

  • On Switch A, use command run show isis route to view IS-IS route table again, route 55.55.55.0/24 has been inserted to Switch A’s routing table with metric value 10. Switch A and Switch C can communicate with each other now.

admin@SwitchA# run show isis route Area instance1: IS-IS L1 IPv4 routing table: Prefix Metric Interface Nexthop Label(s) ---------------------------------------------------------- 33.33.33.0/24 20 vlan1000 192.168.1.2 - 55.55.55.0/24 10 vlan1000 192.168.1.2 - 192.168.1.0/24 20 vlan1000 192.168.1.2 - IS-IS L2 IPv4 routing table: Prefix Metric Interface Nexthop Label(s) ---------------------------------------------------------- 33.33.33.0/24 20 vlan1000 192.168.1.2 - 55.55.55.0/24 10 vlan1000 192.168.1.2 - 192.168.1.0/24 20 vlan1000 192.168.1.2 -

 

 

 

 

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