Configuring BGP Add-Path

BGP Add-Path allows a route reflector (RR) to send two or more routes with the same prefix to a specified IBGP peer. These routes can back up each other or load-balance traffic, which improves network reliability.

Usage Scenario

In a scenario with an RR and clients, if the RR has multiple BGP routes to the same destination (with the same prefix), the RR selects an optimal route from these routes and then sends only the optimal route to its clients. Therefore, the clients have only one route to the destination. If a link along this route fails, route convergence takes a long time, which cannot meet the requirements for high reliability.

To address this issue, deploy the BGP Add-Path feature on the RR. With BGP Add-Path, the RR can send two or more routes with the same prefix to a specified IBGP peer. These routes can back up each other or load-balance traffic, which ensures high reliability in data transmission. The BGP Add-Path feature does not affect BGP route selection rules.

The RR can send Add-Path routes only to IBGP peers.

BGP Add-Path is not supported in BGP confederation scenarios.

Enable BGP Add-Path on the RR, enable the RR to send Add-Path routes to a specified IBGP peer, configure the number of routes that the RR can send to the IBGP peer, and enable the IBGP peer to receive BGP Add-Path routes from the RR so that such routes are available to the IBGP peer. In Figure 1, you can enable BGP Add-Path on the RR, enable Device A to receive BGP Add-Path routes from the RR so that Device A can receive two routes destined for 1.1.1.1/32, with next hops of 172.16.6.2 and 172.16.7.2. The two routes can back up each other or load-balance traffic.

Figure 1 Networking for configuring BGP Add-Path

Pre-configuration Tasks

Before configuring BGP Add-Path, configure basic BGP functions.

Procedure

Perform the following steps on the RR:
1. Run system-view
  The system view is displayed.
2. Run bgp { as-number-plain | as-number-dot }
  The BGP view is displayed.
3. Run bestroute add-path path-number path-number
  BGP Add-Path is enabled, and the number of routes that can be selected is configured.
4. Run peer { ipv4-address | group-name } capability-advertise add-path send
  The device is enabled to send Add-Path routes to the specified peer.
5. Run peer { ipv4-address | group-name } advertise add-path path-number path-number
  The number of routes that the device can send to the peer is configured.
6. Run commit
  The configuration is committed.
Perform the following steps on Device A:
1. Run system-view
  The system view is displayed.
2. Run bgp { as-number-plain | as-number-dot }
  The BGP view is displayed.
3. Run peer { ipv4-address | group-name } capability-advertise add-path receive
  The device is enabled to receive Add-Path routes from the specified peer.
4. Run commit
  The configuration is committed.

Checking the Configurations

Run the following commands on the RR to check configurations:

Run the display bgp peer verbose command to check information about BGP Add-Path.