If a PE receives broadcast traffic from a peer PE, the PE forwards it only to the directly-connected
interfaces of the same VPLS rather than other PEs.
For a packet with the destination MAC address as a non-broadcast address, if a PE cannot identify
this type of the MAC address, the PE broadcasts this packet.
NOTE
Currently, the S9300 supports only the unqualified mode.
Flooding
The Ethernet broadcasts packets with unknown addresses. Therefore, in the VPLS, received
packets with unknown unicast addresses, broadcast addresses, or multicast addresses are flooded
to all the other interface. If multicast needs to be used, PEs adopt other methods such as Internet
Group Management Protocol (IGMP) snooping and Protocol Independent Multicast (PIM)
snooping.
Packet Encapsulation
After a PE discovers its peer, two unidirectional VCs going to opposite directions are established
between a pair of PEs. The two VCs form a bidirectional PW.
There are two modes for encapsulating packets on a VC: Ethernet: Packets encapsulated in
Ethernet mode do not carry any VLAN tag when they are transmitted on the public network.
VLAN: Packets encapsulated in VLAN mode carry VLAN tags when they are transmitted on
the public network.
Access Mode
VLANIF interfaces on a switch can be used as access interfaces of VPLS for forwarding VLAN
packets.
The VLANIF interface on the S9300 is a logical interface rather than a sub-interface of a certain
physical interface. A VLANIF interface contains multiple physical interfaces. That is, VLAN
packets can be received from multiple physical interfaces. The physical interface configured as
a switching interface can send VLAN packets in the following modes:
l Access mode: allows only packets with the default VLAN ID to pass through.
l Trunk mode: allows only packets with a specified VLAN ID to pass through.
HVPLS
The previously mentioned VPLS requires that PEs forward Ethernet frames through fully-
connected Ethernet emulation circuits or PWs. Therefore, all PEs must be connected to each
other in the same VPLS. If there are N PEs on a VPLS network, N x (N - 1)/2 connections are
set up on the VPLS network. When the number of PEs increases, the number of VPLS
connections increases by squares of N.
Hierarchical Virtual Private LAN Service (HVPLS) is thus introduced to address the problem
of the fully-connected VPLS network.
Figure 6-3 shows the HVPLS model.
Quidway S9300 Terabit Routing Switch
Configuration Guide - VPN 6 VPLS Configuration
Issue 03 (2009-08-20) Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
6-5
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