doc: bgp snmp traps <rfc4273|bgp4-mibv2> <enable|disable>

update traps documentation

Signed-off-by: Philippe Guibert <[email protected]>

doc/user/snmptrap.rst

@@ -4,8 +4,9 @@ Handling SNMP Traps
 To handle snmp traps make sure your snmp setup of frr works correctly as
 described in the frr documentation in :ref:`snmp-support`.
 
-The BGP4 mib will send traps on peer up/down events. These should be visible in
-your snmp logs with a message similar to:
+BGP handles both :rfc:`4273` and [Draft-IETF-idr-bgp4-mibv2-11]_ MIBs.
+The BGP4 MIBs will send traps on peer up/down events. These should be
+visible in your snmp logs with a message similar to:
 
 ::
 
@@ -199,3 +200,18 @@ a siren, have your display flash, etc., be creative ;).
 
    # mail the notification
    echo "$MAIL" | mail -s "$SUBJECT" $EMAILADDR
+
+.. _traps-mib-selection:
+
+Traps Mib Selection in BGP
+--------------------------
+
+Both :rfc:`4273` and [Draft-IETF-idr-bgp4-mibv2-11]_ MIBs define traps for
+dealing with up/down events and state transition. The user has the
+possibility to select the MIB he wants to receive traps from:
+
+.. clicmd:: bgp snmp traps <rfc4273|bgp4-mibv2> <enable|disable>
+
+By default, all traps are enabled and sent.
+
+.. [Draft-IETF-idr-bgp4-mibv2-11] <https://tools.ietf.org/id/draft-ietf-idr-bgp4-mibv2-11.txt>