Huawei quidway s7700 - Page 590

Interface-based Layer 2 Protocol Transparent Transmission
Figure 11-2 Networking of interface-based Layer 2 protocol transparent transmission
LAN-B
MSTP
ISP Network
PE1
PE3
PE2
Port based
VLAN 200
Port based
VLAN 300
Port based
VLAN 200
Port based
VLAN 300
Port based
VLAN 200
LAN-A
MSTP
LAN-B
MSTP
LAN-B
MSTP
LAN-A
MSTP
BPDU Tunnel 200
BPDU Tunnel 300
As shown in Figure 11-2, each interface of a PE is connected to one user network. The user
networks connected to the same PE belong to different LANs, namely, LAN-A and LAN-B.
BPDUs sent from user networks are not tagged, but the PE needs to identify the LAN that each
BPDU belongs to. BPDUs of a user network on LAN-A must be forwarded to other user networks
on LAN-A, but cannot be forwarded to user networks on LAN-B. In addition, BPDUs cannot
be processed by network devices of the ISP.
The following methods can be used to meet the proceeding requirements:
l Replace the default multicast MAC address of Layer 2 protocol packets that can be
identified by PEs on the backbone network with another multicast MAC address.
1. Configure all PEs as providers. Then the multicast destination MAC address of
BPDUs sent from the backbone network is changed from 01-80-C2-00-00-00 to
01-80-C2-00-00-08.
2. Configure all devices on user networks as customers. Then the multicast destination
MAC address of BPDUs sent from user networks is 01-80-C2-00-00-00.
3. On PEs, add the interfaces connected to the same user network to the same VLAN.
Then PEs add VLAN tags to received BPDUs according to default VLANs of the
interfaces.
4. PEs (providers) do not consider these packets as Layer 2 protocol BPDUs and do not
send them to the CPU. Instead, PEs select a Layer 2 tunnel to forward the packets
according to the default VLANs of interfaces.
5. Internal nodes on the backbone network forward the packets across the backbone
network as common Layer 2 packets.
Quidway S7700 Smart Routing Switch
Configuration Guide - Ethernet 11 Layer 2 Protocol Transparent Transmission Configuration
Issue 01 (2011-07-15) Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
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