intercepts and processes IGMP request of terminal user and then forwards it to
upper-level router.
3.1.6 L2PT
In QinQ VPN mode, if VPN uses locating at different places want to initiate their L2
protocol for example, STP, LACP, ZDP, they need to use core network to transfer these
L2 protocol messages transparently, and these messages with preserved MAC address
for bridge cannot process transparent transmission normally. L2PT (layer 2 protocol
transportation) solves this problem, so it is widely used to transfer user network L2
protocol message in QinQ VPN.
L2PT networking is as shown in the following figure.
Edge Switches: It locating at the edge of operator network connects customer
network equipment.
Layer 2 protocol transportation port: On port of Edge Switch. The encapsulation of
L2 protocol message.
Transportation PDU: Encapsulated protocol message, for example ZDP, STP and
LACP, etc.
Figure 3-2 L2TP Networking
On the port without initiated L2PT, L2 protocol messages （STP，ZDP，LACP）instead
of being forwarded is either discarded or sent up for protocol processing, which will cause
several blocked stp domains in customer network as per different locations, so that the
entire customer VPN cannot run an integrated STP topology. L2PT transfer BPDU
message transparently in VPN, which helps customers to supply the gap.
The received L2 protocol messages will be encapsulated at the transportation port of
edge switch, then broadcast the encapsulated messages. Initiate remote transportation
switch port to encapsulate these messages.
To Next Page
Loading...
Need help?
General