docs: mention activate keyword in user docs

As of now, the BGP user documentation does not explicitly mention how
to use IPv6. This commit adds documentation of the activate command to
the user documentation which is crucial to get IPv6 networks announced
using FRRouting.

Signed-off-by: Michael Hohl <me@michaelhohl.net>

diff --git a/doc/user/bgp.rst b/doc/user/bgp.rst
index 3572734ba95b249c9dd0e832e4e02cbee0df306b..24c4a7dbf65dd05026f0d300abb22e2ebb130add 100644 (file)
--- a/doc/user/bgp.rst
+++ b/doc/user/bgp.rst
@@ -962,6 +962,56 @@ Networks
    traditional did not check for existence.  For versions 7.4 and beyond
    both traditional and datacenter the network must exist.
 
+.. _ipv6-support:
+
+IPv6 Support
+------------
+
+.. index:: [no] neighbor A.B.C.D activate
+.. clicmd:: [no] neighbor A.B.C.D activate
+
+   This coonfiguration modifies whether to enable an address family for a
+   specific neighbor. By default only the IPv4 unicast address family is
+   enabled.
+
+   .. code-block:: frr
+
+      router bgp 1
+       address-family ipv6 unicast
+        neighbor 2001:0DB8::1 activate
+        network 2001:0DB8:5009::/64
+       exit-address-family
+
+   This configuration example says that network 2001:0DB8:5009::/64 will be
+   announced and enables the neighbor 2001:0DB8::1 to receive this announcement.
+
+.. index:: [no] bgp default ipv4-unicast
+.. clicmd:: [no] bgp default ipv4-unicast
+
+   By default, only the IPv4 unicast address family is announced to all
+   neighbors. Using the 'no bgp default ipv4-unicast' configuration overrides
+   this default so that all address families need to be enabled explicitly.
+
+   .. code-block:: frr
+
+      router bgp 1
+       no bgp default ipv4-unicast
+       neighbor 10.10.10.1 remote-as 2
+       neighbor 2001:0DB8::1 remote-as 3
+       address-family ipv4 unicast
+        neighbor 10.10.10.1 activate
+        network 192.168.1.0/24
+       exit-address-family
+       address-family ipv6 unicast
+        neighbor 2001:0DB8::1 activate
+        network 2001:0DB8:5009::/64
+       exit-address-family
+
+   This configuration demonstrates how the 'no bgp default ipv4-unicast' might
+   be used in a setup with two upstreams where each of the upstreams should only
+   receive either IPv4 or IPv6 annocuments.
+
+
 .. _bgp-route-aggregation:
 
 Route Aggregation