Configuring Promiscuous Peers And Dynamic Peering - Juniper BGP - CONFIGURATION GUIDE V 11.1.X Configuration Manual

BGP speaker to send a notification message to the peer generating the error and to
terminate the session. By default, lenient behavior is disabled.
neighbor lenient

Configuring Promiscuous Peers and Dynamic Peering

You can use the neighbor allow command to enable a peer group to accept incoming
BGP connections from any remote address that matches an access list. Such a peer
group is known as a promiscuous peer group; the member peers are sometimes
referred to as promiscuous peers.
Promiscuous peers are useful when the remote address of the peer is not known
ahead of time. An example is in B-RAS applications, in which interfaces for subscribers
are created dynamically and the remote address of the subscriber is assigned
dynamically from a local pool or by using RADIUS or some other method.
BGP automatically creates a dynamic peer when a peer group member accepts the
incoming BGP connection. Dynamic peers are passive, meaning that when they are
not in the established state, they will accept inbound connections but they will not
initiate outbound connections. You cannot configure any attributes for the dynamic
peers. You cannot remove a dynamic peer with the no neighbor ip-address
command.
When a dynamic peer goes from the established state to the idle state for any reason,
BGP removes the dynamic peer only if it does not go back to the established state
within 1 minute. This delay enables you to see the dynamic peer in show command
output; for example, you might want to see the reason for the last reset or how many
times the session flapped.
While a dynamic peer is not in the established state, the show ip bgp neighbor
command displays the number of seconds remaining until the dynamic peer will be
removed.
If you have configured the neighbor allow command for multiple peer groups, when
an incoming BGP connection matches the access list of more than one of these peer
groups, the dynamic peer is created only in the first peer group. (BGP orders peer
groups alphabetically by name.)
Use to enable a BGP speaker to be more tolerant of some errors generated by a
peer, such as malformed BGP messages or finite state machine errors.
The speaker attempts to recover from the errors and avoid bringing down the
BGP session with the peer.
Lenient behavior is disabled by default.
Example
host1(router-config)#neighbor 10.12.45.23 lenient
Use the no version to restore the default condition, disabling lenient behavior.
See neighbor lenient.
Chapter 1: Configuring BGP Routing
Configuring BGP Peer Groups
47