3Com S7906E Configuration Manual page 1624

Figure 1-1 Network diagram for VPLS
Site 2
CE 3
VPN 1
CE 4
VPN 2
Site 3
MAC address learning and flooding
VPLS provides reachability by MAC address learning. Each PE maintains a MAC address table.
1) Source MAC address learning
MAC address learning includes two parts:
Remote MAC address learning associated with PWs
A PW consists of two unidirectional VC LSPs. A PW is up only when both of the VC LSPs are up. When
the inbound VC LSP learns a new MAC address, the PW needs to map the MAC address to the
outbound VC LSP.
Local MAC address learning of interfaces directly connected with users
This refers to learning source MAC addresses from Layer 2 packets originated by CEs. This occurs on
the corresponding VSI interfaces.
Figure 1-2 shows the procedure of MAC address learning and flooding on PEs.
Tunnel
PW
AC
MPLS backbone
Forwarder
PE 1
PW Signaling
Site 1
VPN 1
CE 1
CE 2
P
PE 2
1-3
VPN 2