create a Virtual Switching Instance (VSI), that provides Ethernet multipoint bridging over a PW mesh. VPLS
network links the VSIs using the MPLS pseudowires to create an emulated Ethernet Switch.
With VPLS, all customer equipment (CE) devices participating in a single VPLS instance appear to be on the
same LAN and, therefore, can communicate directly with one another in a multipoint topology, without
requiring a full mesh of point-to-point circuits at the CE device. A service provider can offer VPLS service
to multiple customers over the MPLS network by defining different bridged domains for different customers.
Packets from one bridged domain are never carried over or delivered to another bridged domain, thus ensuring
the privacy of the LAN service.
VPLS transports Ethernet IEEE 802.3, VLAN IEEE 802.1q, and VLAN-in-VLAN (q-in-q) traffic across
multiple sites that belong to the same Layer 2 broadcast domain. VPLS offers simple VLAN services that
include flooding broadcast, multicast, and unknown unicast frames that are received on a bridge. The VPLS
solution requires a full mesh of pseudowires that are established among PE routers. The VPLS implementation
is based on Label Distribution Protocol (LDP)-based pseudowire signaling.
VPLS for Layer 2 Switching
VPLS technology includes the capability of configuring the Cisco ASR 9000 Series Routers to perform Layer
2 bridging. In this mode, the Cisco ASR 9000 Series Routers can be configured to operate like other Cisco
switches.
These features are supported:
• Bridging IOS XR Trunk Interfaces
• Bridging on EFPs
Refer to the Configuration Examples for Multipoint Layer 2 Services section for examples on these bridging
features.
VPLS Discovery and Signaling
VPLS is a Layer 2 multipoint service and it emulates LAN service across a WAN service. VPLS enables
service providers to interconnect several LAN segments over a packet-switched network and make it behave
as one single LAN. Service provider can provide a native Ethernet access connection to customers using
VPLS.
The VPLS control plane consists of two important components, autodiscovery and signaling:
• VPLS Autodiscovery eliminates the need to manually provision VPLS neighbors. VPLS Autodiscovery
enables each VPLS PE router to discover the other provider edge (PE) routers that are part of the same
VPLS domain.
• Once the PEs are discovered, pseudowires (PWs) are signaled and established across each pair of PE
routers forming a full mesh of PWs across PE routers in a VPLS domain
Figure 19: VPLS Autodiscovery and Signaling
L2VPN and Ethernet Services Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.3.x
208
Implementing Multipoint Layer 2 Services
VPLS for Layer 2 Switching
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