Configuring BGP-LS

BGP-LS provides a simple and efficient method of collecting topology information.

Usage Scenario

Without BGP-LS, the router uses an IGP (OSPF or IS-IS) to collect network topology information and report the topology information of each area to the controller separately. This method has the following disadvantages:

The controller must have high computing capabilities and support the IGP and its algorithm.
The controller cannot gain the complete inter-area topology information and therefore is unable to calculate optimal E2E paths.
Different IGPs report topology information separately to the controller, which complicates the controller's analysis and processing.

With powerful route selection capabilities of BGP, BGP-LS has the following advantages:

Reduces computing capability requirements and spares the necessity of IGPs on the controller.
Facilitates route selection and calculation on the controller by using BGP to summarize process or AS topology information and report the complete information to the controller.
Requires only one routing protocol (BGP) to report topology information to the controller.

BGP-LS needs to be deployed on the devices connected to the controller.

Pre-configuration Tasks

Before configuring BGP-LS, configure basic IPv4 IS-IS functions or basic OSPF functions.

Procedure

Enable IGP topology advertisement to BGP. You can determine to enable IS-IS topology advertisement to BGP or OSPF topology advertisement to BGP based on network configurations.
- Enable IS-IS topology advertisement to BGP.
  1. Run system-view
    The system view is displayed.
  2. Run isis [ process-id ]
    An IS-IS process is configured.
  3. Run bgp-ls enable [ level-1 | level-2 | level-1–2 ]
    IS-IS topology advertisement to BGP is enabled.
    
    To enable IS-IS to advertise the topology of a Level-1 area and filter the route prefixes leaked from a Level-2 area to the Level-1 area, run the bgp-ls enable level-1 level-2-leaking-route-ignore command.
  4. (Optional) Run bgp-ls identifier identifier-value
    A BGP-LS identifier is configured.
  5. Run commit
    The configuration is committed.
- Enable OSPF topology advertisement to BGP.
  1. Run system-view
    The system view is displayed.
  2. Run ospf [ process-id | router-idrouter-id | vpn-instancevpn-instance-name ] ^*
    An OSPF process is configured.
  3. Run bgp-ls enable
    OSPF topology advertisement to BGP is enabled.
  4. (Optional) Run bgp-ls identifier identifier-value
    A BGP-LS identifier is configured.
  5. Run commit
    The configuration is committed.
Enable BGP-LS.
1. Run system-view
  The system view is displayed.
2. Run bgp { as-number-plain | as-number-dot }
  BGP is enabled, and the BGP view is displayed.
3. Run peer { group-name | ipv4-address } as-number { as-number-plain | as-number-dot }
  
  The IP address and AS number of a BGP peer are specified.
4. Run link-state-family unicast
  BGP-LS is enabled, and the BGP-LS address family view is displayed.
5. Run peer { group-name | ipv4-address } enable
  BGP-LS route exchange with the specified peer or peer group is enabled.
6. (Optional) Run domain identifier domain-id
  
  A BGP-LS domain ID is configured.
  
  A BGP-LS domain ID identifies a device with BGP-LS enabled. If no BGP-LS domain ID is configured, a BGP router ID is used as the BGP-LS domain ID by default. The same BGP-LS domain ID can be configured for multiple devices so that the controller calculates routes based on the combined topology information reported by the devices.
7. (Optional) Run domain as { domain as-plain | domain as-dot }
  
  A BGP-LS domain AS number is configured.
  
  Two devices with different BGP AS numbers must have the same BGP-LS domain AS number configured using the domain as command so that the controller can obtain combined topology information about the two ASs for route calculation.
8. (Optional) Run peer { group-name | ipv4-address } reflect-client
  
  An RR is configured, and an RR client is specified.
  
  The router on which the peer reflect-client command is run functions as the RR, and the specified peer or peer group functions as a client.
  
  If the clients of an RR are fully meshed, you can run the undo reflect between-clients command to disable route reflection among these clients through the RR to reduce bandwidth consumption.
  
  If a cluster has multiple RRs configured, you can run the reflector cluster-id cluster-id command to configure the same cluster ID for all the RRs. This command is applicable only to RRs.
9. (Optional) Run peer { group-name | ipv4-address } route-limitlimit [ percentage ] [ alert-only | idle-forever | idle-timeoutminutes ]
  
  The maximum number of BGP-LS routes that the local device can receive from a specified peer is set.
  
  In most cases, the BGP-LS routing table contains a large number of BGP-LS routes. If a lot of BGP-LS routes are received from peers, excessive system resources will be consumed. To minimize system resource consumption, you can configure the maximum number of routes that the router can receive from a BGP-LS peer.
10. (Optional) Run peer { group-name | ipv4-address } route-policyroute-policy-name { import | export }
  
  A route-policy is specified for the BGP-LS routes to be received from or advertised to a specified BGP peer or peer group.
  
  After a route-policy is created, you can run the peer route-policy command to use the route-policy to filter the BGP-LS routes to be received from or advertised to a specified BGP peer or peer group. The command configuration ensures that only desired routes are accepted or advertised, which helps manage routes and reduces the BGP-LS routing table size and system resource consumption.
11. (Optional) Run peer { group-name | ipv4-address } route-update-intervalinterval
  
  An interval at which the device sends Update messages carrying the same route prefix to a specified peer or peer group is set.
  
  When BGP-LS routes change, the router sends Update messages to notify its peers. If a route changes frequently, to prevent the router from sending Update messages for every change, run this command to set an interval at which the router sends Update messages carrying the same route prefix to a specified peer or peer group.
12. Run commit
  The configuration is committed.

Verifying the Configuration

After configuring BGP-LS, verify the configuration.

Run the display bgp link-state unicast peer command to check information about BGP-LS peers and their status.
Run the display bgp link-state unicast routing-table command to check BGP-LS route information.
Run the display bgp link-state unicast routing-table statistics command to check BGP-LS route statistics.