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

Before completing this task, the set of paths eligible for selection as additional-paths must be configured by using the additional-paths select command, under the relevant address family. An example is provided at the end of this task that shows all the configuration steps in order.

BGP additional-paths is supported for the following BGP address families:
  • IPv4 unicast
  • IPv4 unicast VRF
  • IPv6 unicast
  • IPv6 unicast VRF

Perform the following task to enable additional-paths on a specific peer device and to specify the additional routes to be advertised by the peer, under the IPv4 unicast address family.

  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

    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    ---

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

After completing this task, restart the BGP session to activate the new additional-paths capability configuration.

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