The 7750 SR, 7450 ESS, or 7950 XRS generates this route type for advertising B-MAC addresses for the following:
Learned MACs on B-SAPs or B-SDP bindings - if mac-advertisement is enabled.
Conditional static MACs - if mac-advertisement is enabled.
B-VPLS shared B-MACs (source-bmacs) and dedicated B-MACs (es-bmacs).
The route type 2 generated by the router uses the following fields and values:
Route Distinguisher—Taken from the RD of the VPLS service within the BGP context. The RD can be configured or derived from the bgp-evpn evi value.
Ethernet Segment Identifier (ESI):
ESI = 0 for the advertisement of source-bmac, es-bmacs, sap-bmacs, or sdp-bmacs if no multi-homing or single-active multi-homing is used.
ESI=MAX-ESI (0xFF..FF) in the advertisement of es-bmacs used for all-active multi-homing.
ESI different from zero or MAX-ESI for learned B-MACs on B-SAPs/SDP bindings if EVPN multi-homing is used on B-VPLS SAPs and SDP bindings.
Ethernet Tag ID: 0.
MAC address length: always 48.
B-MAC Address learned, configured, or system-generated.
IP address length zero and IP address omitted.
MPLS Label 1: carries the MPLS label allocated by the system to the B-VPLS service. The label value is encoded in the high-order 20 bits of the field and is the same label used in the routes type 3 for the same service unless BGP-EVPN MPLS ingress-replication-bum-label is configured in the service.
The MAC Mobility extended community:
The MAC mobility extended community is used in PBB-EVPN for C-MAC flush purposes if per ISID load balancing (single-active multi-homing) is used and a source-bmac is used for traffic coming from the ESI.
If there is a failure in one of the ES links, C-MAC flush through the withdrawal of the B-MAC cannot be done (other ESIs are still working); therefore, the MAC mobility extended community is used to signal C-MAC flush to the remote PEs.
When a dedicated es-bmac per ESI is used, the MAC flush can be based on the withdrawal of the B-MAC from the failing node.
es-bmacs are advertised as static (sticky bit set).
Source-bmacs are advertised as static MACs (sticky bit set). In the case of an update, if advertised to indicate that C-MAC flush is needed, the MAC mobility extended community is added to the B-MAC route including a higher sequence number (than the one previously advertised) in addition to the sticky bit.