Configuring additional-paths and advertisement of additional-paths at peer group level

Before completing this task, configure (by using the additional-paths select command) the set of paths eligible for selection as additional-paths 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 for a specific peer group and specify the additional routes for the peer group to advertise, under the IPv4 unicast address family.

From privileged EXEC mode, enter global configuration mode.
```
device# configure terminal
```
Enable BGP routing.
```
device(config)# router bgp
```
Create a peer group. The following example shows how to create a peer group named pg-1
```
device(config-bgp)# neighbor pg-1 peer-group
```
Enter IPv4 unicast address family configuration mode.
```
device(config-bgp)# address-family ipv4 unicast 
```
Enable additional-paths for the peer group.
```
device(config-bgp-ipv4u)# neighbor pg-1 additional-paths receive send
```
This example enables the capability to both receive and send additional-paths on peer group pg-1.
Note
Changes in the capability of receiving or sending additional-paths are reflected only after the BGP session is restarted.
Configure the additional-paths to be advertised by the peer group. The following example shows how to configure the advertisement of group-best paths.
```
device(config-bgp-ipv4u)# neighbor pg-1 additional-paths advertise group-best
```
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.

The following example first shows how to configure group-best paths as candidates for selection as additional paths, under the IPv4 address family. It then shows how to enable receiving and sending additional-paths for peer group pg-1 and configures the advertisement of group-best paths for pg-1.

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

device(config-bgp)# neighbor pg-1 peer-group
device(config-bgp)# address-family ipv4 unicast 
device(config-bgp-ipv4u)# neighbor pg-1 additional-paths receive send
device(config-bgp-ipv4u)# neighbor pg-1 additional-paths advertise group-best

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