Huawei Quidway S9300 Configuration Manual page 242

9 BPDU Tunnel Configuration
Generally, a PE device functions as a convergence device. As shown in
convergence port on PE1 can receive BPDUs from LAN-A and LAN-B. BPDUs sent from a CE
device to a PE device must contain VLAN tags so that the PE can distinguish BPDUs from the
two LANs. In
BPDUs sent by a device that runs RSTP or MSTP do not contain VLAN tags. When the CPU
of the device receives BPDUs with VLAN tags, the system considers these BPDUs as invalid
packets and discards them. If the PE device supports the VLAN-based BPDU tunnel, BPDUs
are transmitted across the Layer 2 network to the user network through the BPDU tunnel instead
of being sent to the CPU.
One solution is to configure different roles for the devices of the ISP and user networks.
1.
2.
3.
4.
As shown in
BPDUs with VLAN ID 200 across the ISP network through the BPDU tunnel of VLAN 200.
PE2 then forwards the BPDUs to LAN-A connected to PE2 and calculates the spanning tree.
BPDUs sent from LAN-B contains VLAN ID 100. PE1 forwards BPDUs with VLAN ID 100
across the ISP network through the BPDU tunnel of VLAN 100. PE2 then forwards the BPDUs
to LAN-B connected to PE2 and calculates the spanning tree.
Another solution is to configure the devices of the ISP and user networks as the same role. That
is, configure all the devices as providers or customers. The implementation of this solution is
similar to the implementation of the preceding solution. In this solution, you need to replace
01-80-C2-00-00-00 with a multicast MAC address and enable BPDU tunnel on the ports of the
ISP devices connected to devices of user networks.
QinQ-based BPDU Tunnel
l
9-6
Figure 9-4, VLAN ID of LAN-A is 200; VLAN ID of LAN-B is 100.
Configure the ISP devices, that is, the PE devices, as providers. Thus, the destination MAC
address of the BPDUs sent from the ISP network is changed from 01-80-C2-00-00-00 to
01-80-C2-00-00-08.
Configure all devices on the user networks as customers. Thus, the destination MAC
address of the BPDUs sent from user networks is still 01-80-C2-00-00-00.
Configure BPDUs sent from a CE device to a PE device to contain the specified VLAN
ID.
Configure the PE interfaces connected to CE devices to forward the BPDUs with the
specified VLAN ID. The destination MAC address of the BPDUs sent from user networks
is 01-80-C2-00-00-00 rather than 01-80-C2-00-00-08. Thus, the PE devices (providers) do
not consider the BPDUs sent from user networks as BPDUs. The PE devices choose BPDU
tunnels to forward the BPDUs according to the PVIDs of the BPDUs instead of sending
the BPDUs to their CPUs.
Finally, the BPDUs are transparently transmitted across the ISP network.
Figure 9-4, BPDUs sent from LAN-A contains VLAN ID 200. PE1 forwards
QinQ overview
The QinQ protocol is a Layer 2 tunneling protocol based on IEEE 802.1Q. The QinQ
technology improves the utilization of VLANs by adding another 802.1Q tag to a packet.
In this manner, services in the private VLAN can be transparently transmitted to the public
network. A packet transmitted on the backbone network has two 802.1q tags (a public tag
and a private tag), that is, 802.1Q-in-802.1Q. Therefore, the packet is called a QinQ packet.
Figure 9-5 shows the format of a QinQ packet. Compared with an 802.1Q packet, a QinQ
packet contains an additional tag following the source address (SA) field. This tag is called
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Quidway S9300 Terabit Routing Switch
Configuration Guide - Ethernet
Figure
Issue 03 (2009-08-20)
9-4, the