Configuring BGP additional-paths and additional-path advertisement at neighbor level

BGP additional-paths can be enabled for a specific peer device (neighbor) under a BGP address family. In addition, configuration options are available to control the additional-paths that are advertised to neighbors.

1. From privileged EXEC mode, enter global configuration mode.
   

   device# configure terminal
   

2. Enable BGP routing.
   

   device(config)# router bgp
   

3. Enter IPv4 unicast address family configuration mode.
   

   device(config-bgp)# address-family ipv4 unicast 
   

4. Enable additional-paths for a specific peer.
   

   device(config-bgp-ipv4u)# neighbor 10.60.60.20 additional-paths receive send
   

   This example enables the capability to both receive and send additional-paths on peer device 10.60.60.20.

   

   Note

   Changes in the capability of receiving or sending additional-paths are reflected only after the BGP session is restarted.
5. Configure the additional-paths to be advertised by the peer.
   

   device(config-bgp-ipv4u)# neighbor 10.60.60.20 additional-paths advertise all
   

   Paths configured for advertisement to neighbors must be a subset of the paths previously configured by using the additional-paths select command under the IPv4 address family.
6. Verify the configuration.
   

   device# show ip bgp neighbors
   
       '+': Data in InQueue '>': Data in OutQueue '-': Clearing
       '*': Update Policy 'c': Group change 'p': Group change Pending
       'r': Restarting 's': Stale '^': Up before Restart '<': EOR waiting
   
   1   IP Address: 10.60.60.20, AS: 200 (IBGP), RouterID: 10.60.60.20, VRF: default-vrf
       State: ESTABLISHED, Time: 4h3m28s, KeepAliveTime: 60, HoldTime: 180
          KeepAliveTimer Expire in 0 seconds, HoldTimer Expire in 159 seconds
       Minimal Route Advertisement Interval: 0 seconds
          RefreshCapability: Received
       Address Family : IPV4 Unicast
          Configured with Add-Path(send receive)capability
          Received Add-Path (send receive)capability in open msg
          Negotiated Add-Path(send receive)capability
       Messages:    Open        Update      KeepAlive   Notification   Refresh-Req
          Sent    : 1           1           275         0              0
          Received: 1           1           275         0              0
       Last Update Time: NLRI       Withdraw          NLRI       Withdraw
                     Tx: 4h3m28s    ---           Rx: 4h3m28s    ---
   

Example

The following example first shows how to configure all paths as eligible for selection as additional-paths under the IPv4 address family. It then shows how to enable receiving and sending additional-paths on a specific peer device (10.60.60.20) and configures the advertisement of all paths by 10.60.60.20.

device# configure terminal
device(config)# router bgp
device(config-bgp)# address-family ipv4 unicast
device(config-bgp-ipv4u)# additional-paths select all

device(config-bgp-ipv4u)# neighbor 10.60.60.20 additional-paths receive send
device(config-bgp-ipv4u)# neighbor 10.60.60.20 additional-paths advertise all