(links connecting customer devices to the PEs). Then, the MAC addresses are distributed over MPLS using
BGP with an MPLS label identifying the EVPN instance.
PBB-EVPN Overview
The PBB-EVPN solution combines Ethernet Provider Backbone Bridging (PBB - IEEE 802.1ah) with Ethernet
VPN where, PEs perform as PBB Backbone Edge Bridge (BEB). The PEs receive 802.1Q Ethernet frames
from their attachment circuits. These frames are encapsulated in the PBB header and forwarded over the
IP/MPLS core. On the egress side (EVPN PE), the PBB header is removed after MPLS disposition, and the
original 802.1Q Ethernet frame is delivered to the customer equipment.
Figure 46: PBB-EVPN Network
The PE routers perform these functions:
• Learns customer or client MAC addresses (C-MACs) over the attachment circuits in the data-plane, per
normal bridge operation.
• Learns remote C-MAC to backbone MAC (B-MAC) bindings in the data-plane from traffic ingress from
the core.
• Advertises local B-MAC address reachability information in BGP to all other PE nodes in the same set
of service instances. Note that every PE has a set of local B-MAC addresses that uniquely identify the
device.
• Builds a forwarding table from the received remote BGP advertisements, associating remote B-MAC
addresses with remote PE IP addresses.
PBB-EVPN scales well for large network with millions of customer MAC addresses by constraining customer
MAC address in access. Only B-MAC addresses are advertised in core, making the number of BGP routes
exchanged manageable.
For PBB EVPN, the B-MAC flush is per B-MAC per Ethernet VPN Instance (EVI).
L2VPN and Ethernet Services Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.3.x
364
Implementing IEEE 802.1ah Provider Backbone Bridge
PBB-EVPN Overview
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