doc: add neighbor PEER capability fqdn command

improve bgp doc

Signed-off-by: Francois Dumontet <[email protected]>

doc/user/bgp.rst

@@ -1792,6 +1792,18 @@ Configuring Peers
    This includes changing graceful-restart (LLGR also) timers,
    enabling/disabling add-path, and other supported capabilities.
 
+.. clicmd:: neighbor PEER capability fqdn 
+
+   Allow BGP to negotiate the FQDN Capability with its peers.
+
+   FQDN Capability defines a new BGP message (CAPABILITY) allowing the
+   use of peer's name and domain name.
+
+   This capability is activated by default. The ``no neighbor PEER capability
+   fqdn`` avoid negotiation of that capability. This is useful for peers who
+   are not supporting this capability or supporting BGP Capabilities 
+   Negotiation RFC 2842.
+
 .. clicmd:: neighbor <A.B.C.D|X:X::X:X|WORD> accept-own
 
    Enable handling of self-originated VPN routes containing ``accept-own`` community.
@@ -2121,7 +2133,6 @@ Capability Negotiation
 
 .. clicmd:: neighbor PEER strict-capability-match
 
-
    Strictly compares remote capabilities and local capabilities. If
    capabilities are different, send Unsupported Capability error then reset
    connection.