doc: Document `neighbox X local-as Y replace-as no-prepend dual-as`

Signed-off-by: Donatas Abraitis <donatas@opensourcerouting.org>

diff --git a/doc/user/bgp.rst b/doc/user/bgp.rst
index b6d289fac9292b72552b5dde1b2ecea2810c6316..69a77568c6972b0433e1506ad56c9d36f7eca82b 100644 (file)
--- a/doc/user/bgp.rst
+++ b/doc/user/bgp.rst
@@ -1818,7 +1818,7 @@ Configuring Peers
    Since sent prefix count is managed by update-groups, this option
    creates a separate update-group for outgoing updates.
 
-.. clicmd:: neighbor PEER local-as AS-NUMBER [no-prepend] [replace-as]
+.. clicmd:: neighbor PEER local-as AS-NUMBER [no-prepend [replace-as [dual-as]]]
 
    Specify an alternate AS for this BGP process when interacting with the
    specified peer. With no modifiers, the specified local-as is prepended to
@@ -1834,6 +1834,10 @@ Configuring Peers
 
    Note that replace-as can only be specified if no-prepend is.
 
+   The ``dual-as`` keyword is used to configure the neighbor to establish a peering
+   session using the real autonomous-system number (``router bgp ASN``) or by using
+   the autonomous system number configured with the ``local-as``.
+
    This command is only allowed for eBGP peers.
 
 .. clicmd:: neighbor <A.B.C.D|X:X::X:X|WORD> as-override