R21xx-HP FlexFabric 11900 MPLS Configuration Guide

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single Layer 2 VPN, which is referred to as a "VPLS instance." Sites in different VPLS instances
cannot communicate with each other at Layer 2.
• VSI—A virtual switch instance provides Layer 2 switching services for a VPLS instance on a PE. A VSI
acts as a virtual switch that has all the functions of a conventional Ethernet switch, including source
MAC address learning, MAC address aging, and flooding. VPLS uses VSIs to forward Layer 2 data
packets in VPLS instances.
VPLS implementation
Creating a PW
To create a PW between PEs in the same VPLS instance, follow these steps:
1. Manually specify the address of the peer PE.
2. Configure PW labels manually, or automatically through LDP.
{ Manual configuration: On each PE, assign an incoming label and an outgoing label to create
the PW.
{ Automatic configuration: On each PE, configure LDP to assign and advertise the PW label to
the peer PE to establish a unidirectional LSP. The two unidirectional LSPs between the PEs form
a PW.
If the PW is carried on an LSP or MPLS TE tunnel, each packet on the PW contains two labels. The
inner label is the PW label, which identifies the PW of the packet and makes sure the packet is
forwarded to the correct VSI. The outer label is the public LSP or MPLS TE tunnel label, which makes
sure the packet is correctly forwarded between the PEs.
MAC address learning, aging, and withdrawal
VPLS provides reachability through source MAC learning. A PE maintains a MAC address table for each
VSI.
As shown in Figure 72, a P
E learns source MAC addresses in the following ways:
• Learning the source MAC addresses of directly connected sites
If the source MAC address of a packet from a CE does not exist in the MAC address table, the PE
learns the source MAC address on the AC connected to the CE.
• Learning the source MAC addresses of remote sites connected through PWs
A VSI regards a PW as a logical Ethernet interface. If the source MAC address of a packet
received from a PW does not exist in the MAC address table, the PE learns the source MAC
address on the PW of the VSI.