In enterprise IP VPNs, BGP is often used to exchange routing information, for example between headquarter and branch offices. ESM dynamic BGP peering is needed when a residential access connection provides IP connectivity to the enterprise router.
An ESM dynamic BGP peer setup is automatic when a BGP peering policy attribute is received during RADIUS authentication of a routed subscriber host. The BGP peer is torn down and the associated routes removed from the routing table when the subscriber host is removed from the system (for example, because of a lease timeout or log out).
An ESM dynamic BGPv4 peer supports the IPv4 address family to exchange IPv4 routes and an ESM dynamic BGPv6 peer supports the IPv6 address family to exchange IPv6 routes. When both IPv4 and IPv6 routes must be exchanged, dual-stack routed subscriber sessions require two dynamic BGP peers, one for each address family.
ESM dynamic BGP peering is supported for routed subscriber hosts terminated in a VPRN service and is not supported for hosts terminated in an IES service. ESM dynamic BGP peering is supported in a wholesale and retail deployment.
The BGP learned routes scaling is limited by the BGP scaling limits. The routes learned by a dynamic BGP peer are populated in the routing table as remote BGP routes.
Multi-Chassis Synchronization (MCS) supports the synchronization of BGP peering policy and peering parameters. BGP learned routes are not synchronized and must be relearned after a redundancy failover. To ensure subscriber prefix matching between the active and standby BNG for SLAAC hosts, use static prefix assignment.