Example for Configuring IS-IS to Interact with BGP

This section describes how to configure IS-IS to interact with BGP, including configuring BGP and IS-IS to import routes from each other.

Networking Requirements

In Figure 1:

  • Device A and Device B belong to the same AS, and the IS-IS neighbor relationship is established between the two devices. BGP is not enabled on Device A.

  • An EBGP connection is established between Device B and Device C. When IS-IS imports BGP routes, a routing policy is required to change the route cost.

Figure 1 Configuring IS-IS to interact with BGP

Device Name

Interface

IP Address

Device A

GE0/1/0

10.1.1.1/24

Device B

Loopback0

192.168.0.1/32

GE0/1/0

10.1.1.2/24

GE0/1/8

10.2.1.1/24

Device C

Loopback0

192.168.0.2/32

GE0/1/0

10.2.1.2/24

Configuration Roadmap

The configuration roadmap is as follows:

  1. Enable IS-IS and specify NETs on device A and device B.

  2. Configure an EBGP connection on device B and device C.

  3. Configure IS-IS and BGP to import routes from each other on Device B, and then check the routes.

Data Preparation

To complete the configuration, you need the following data:

  • Area addresses of Device A and Device B

  • Router ID and AS number of Device B

  • Router ID and AS number of Device C

Procedure

  1. Configure an IP address for each interface. For configuration details, see Configuration Files in this section.
  2. Configure basic IS-IS functions.

    # Configure Device A.

    [~DeviceA] isis 1
[*DeviceA-isis-1] network-entity 10.0000.0000.0001.00
[*DeviceA-isis-1] quit
[*DeviceA] interface gigabitethernet 0/1/0
[*DeviceA-GigabitEthernet0/1/0] isis enable 1
[*DeviceA-GigabitEthernet0/1/0] commit
[~DeviceA-GigabitEthernet0/1/0] quit

    # Configure Device B.

    [~DeviceB] isis 1
[*DeviceB-isis-1] network-entity 10.0000.0000.0002.00
[*DeviceB-isis-1] quit
[*DeviceB] interface gigabitethernet 0/1/0
[*DeviceB-GigabitEthernet0/1/0] isis enable 1
[*DeviceB-GigabitEthernet0/1/0] commit
[~DeviceB-GigabitEthernet0/1/0] quit

  3. Configure an EBGP connection.

    # Configure Device B.

    [~DeviceB] bgp 65008
[*DeviceB-bgp] router-id 1.1.1.1
[*DeviceB-bgp] peer 10.2.1.2 as-number 65009
[*DeviceB-bgp] ipv4-family unicast
[*DeviceB-bgp-af-ipv4] network 10.2.1.0 255.255.255.0
[*DeviceB-bgp-af-ipv4] commit

    # Configure Device C.

    [~DeviceC] bgp 65009
[*DeviceC-bgp] router-id 2.2.2.2
[*DeviceC-bgp] peer 10.2.1.1 as-number 65008
[*DeviceC-bgp] ipv4-family unicast
[*DeviceC-bgp-af-ipv4] network 10.2.1.0 255.255.255.0
[*DeviceC-bgp-af-ipv4] commit

  4. Configure IS-IS to import BGP routes.

    # Configure a static route on Device C.

    [~DeviceC] ip route-static 172.16.1.1 32 NULL 0
[*DeviceC] commit

    # On Device C, configure BGP to import the static route.

    [~DeviceC] bgp 65009
[~DeviceC-bgp] import-route static
[*DeviceC-bgp] commit

    # On Device B, configure IS-IS to import the BGP route.

    [~DeviceB] isis 1
[~DeviceB-isis-1] import-route bgp
[*DeviceB-isis-1] commit
[~DeviceB-isis-1] quit

    # Display the routing table of Device A. The command shows that IS-IS successfully imports the BGP route 172.16.1.1/32.

    [~DeviceA] display ip routing-table
Route Flags: R - relay, D - download to fib, T - to vpn-instance, B - black hole route
------------------------------------------------------------------------------
Routing Table: _public_
         Destinations : 11        Routes : 11

Destination/Mask    Proto  Pre  Cost     Flags NextHop         Interface

       10.1.1.0/24  Direct 0    0           D  10.1.1.1        GigabitEthernet0/1/0
       10.1.1.1/32  Direct 0    0           D  127.0.0.1       GigabitEthernet0/1/0
     10.1.1.255/32  Direct 0    0           D  10.1.1.2        GigabitEthernet0/1/0
       127.0.0.0/8  Direct 0    0           D  127.0.0.1       InLoopBack0
      127.0.0.1/32  Direct 0    0           D  127.0.0.1       InLoopBack0
127.255.255.255/32  Direct 0    0           D  127.0.0.1       InLoopBack0
    172.16.1.1/32  ISIS-L2 15  74          D  10.1.1.2        GigabitEthernet0/1/0
255.255.255.255/32  Direct 0    0           D  127.0.0.1       InLoopBack0

    # On Device B, configure the AS_Path filter, and apply the filter in the routing policy named RTC.

    [~DeviceB] ip as-path-filter 1 permit 65009
[*DeviceB] route-policy RTC permit node 0
[*DeviceB-route-policy] if-match as-path-filter 1
[*DeviceB-route-policy] apply cost 20
[*DeviceB-route-policy] commit
[~DeviceB-route-policy] quit

    # On Device B, configure IS-IS to import the BGP route.

    [~DeviceB] isis 1
[~DeviceB-isis-1] import-route bgp route-policy RTC
[*DeviceB-isis-1] commit
[~DeviceB-isis-1] quit

    # Display the routing table of device A. The command shows that the AS_Path filter has been applied and that the cost of the imported route 172.16.1.1/32 changes from 74 to 94.

    [~DeviceA] display ip routing-table
Route Flags: R - relay, D - download to fib, T - to vpn-instance, B - black hole route
------------------------------------------------------------------------------
Routing Table: _public_
         Destinations : 11        Routes : 11

Destination/Mask    Proto  Pre  Cost     Flags NextHop         Interface

       10.1.1.0/24  Direct 0    0           D  10.1.1.1        GigabitEthernet0/1/0
       10.1.1.1/32  Direct 0    0           D  127.0.0.1       GigabitEthernet0/1/0
     10.1.1.255/32  Direct 0    0           D  10.1.1.2        GigabitEthernet0/1/0
       127.0.0.0/8  Direct 0    0           D  127.0.0.1       InLoopBack0
      127.0.0.1/32  Direct 0    0           D  127.0.0.1       InLoopBack0
127.255.255.255/32  Direct 0    0           D  127.0.0.1       InLoopBack0
    172.16.1.1/32  ISIS-L2 15  94          D  10.1.1.2        GigabitEthernet0/1/0
255.255.255.255/32  Direct 0    0           D  127.0.0.1       InLoopBack0

  5. Configure BGP to import IS-IS routes.

    [~DeviceB] bgp 65008
[~DeviceB-bgp] import-route isis 1
[*DeviceB-bgp] commit
[~DeviceB-bgp] quit

    # Display the routing table of Device C. The command shows that BGP has imported the IS-IS route 10.1.1.0/24.

    [~DeviceC] display ip routing-table
Route Flags: R - relay, D - download to fib, T - to vpn-instance, B - black hole route
------------------------------------------------------------------------------
Routing Table: _public_
         Destinations : 7        Routes : 7

Destination/Mask    Proto  Pre  Cost     Flags NextHop         Interface

        192.168.0.2/32  Direct  0    0             D   127.0.0.1       LoopBack0
       10.1.1.0/24  EBGP    255  0             D   10.2.1.1        GigabitEthernet0/1/0
       10.2.1.0/24  Direct  0    0             D   10.2.1.2        GigabitEthernet0/1/0
       10.2.1.2/32  Direct  0    0             D   127.0.0.1       GigabitEthernet0/1/0
     10.2.1.255/32  Direct  0    0             D   127.0.0.1       GigabitEthernet0/1/0
      127.0.0.0/8   Direct  0    0             D   127.0.0.1       InLoopBack0
      127.0.0.1/32  Direct  0    0             D   127.0.0.1       InLoopBack0
127.255.255.255/32  Direct  0    0             D   127.0.0.1       InLoopBack0
     172.16.1.1/32  Static  60   0             DB  0.0.0.0         NULL0
    192.168.0.1/32  EBGP    255  0             RD  10.2.1.1        GigabitEthernet0/1/0
255.255.255.255/32  Direct  0    0             D   127.0.0.1       InLoopBack0

Configuration Files

  • Device A configuration file

    #
sysname DeviceA
#
isis 1
 network-entity 10.0000.0000.0001.00
#
interface GigabitEthernet0/1/0
 undo shutdown
 ip address 10.1.1.1 255.255.255.0
 isis enable 1
#
return

  • Device B configuration file

    #
sysname DeviceB
#
isis 1
 import-route bgp route-policy RTC
 network-entity 10.0000.0000.0002.00
#
interface GigabitEthernet0/1/0
 undo shutdown
 ip address 10.1.1.2 255.255.255.0
 isis enable 1
#
interface GigabitEthernet0/1/8
 undo shutdown
 ip address 10.2.1.1 255.255.255.0
#
interface LoopBack0
 ip address 192.168.0.1 255.255.255.255
#
bgp 65008
 router-id 1.1.1.1
 peer 10.2.1.2 as-number 65009
 #
 ipv4-family unicast
  undo synchronization
  network 10.2.1.0 255.255.255.0
  import-route static
  import-route isis 1
  peer 10.2.1.2 enable
#
route-policy RTC permit node 0
 if-match as-path-filter 1
 apply cost 20
#
ip as-path-filter 1 permit 65009
#
return

  • Device C configuration file

    #
sysname DeviceC
#
interface GigabitEthernet0/1/0
 undo shutdown
 ip address 10.2.1.2 255.255.255.0
#
interface LoopBack0
 ip address 192.168.0.2 255.255.255.255
#
bgp 65009
 router-id 2.2.2.2
 peer 10.2.1.1 as-number 65008
 #
 ipv4-family unicast
  undo synchronization
  network 10.2.1.0 255.255.255.0
  import-route static
  peer 10.2.1.1 enable
#
ip route-static 172.16.1.1 255.255.255.255 NULL0
#
return
Parent Topic: IS-IS Configuration Examples
Copyright © Huawei Technologies Co., Ltd.
Copyright © Huawei Technologies Co., Ltd.
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