ZyXEL Communications GS2200-24P Series, User Manual, Page: 252 / 360

Chapter 27 Layer 2 Protocol Tunneling
GS2200-24/24P User’s Guide
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In the following example, if you enable L2PT for STP, you can have switches A, B,
C and D in the same spanning tree, even though switch A is not directly
connected to switches B, C and D. Topology change information can be
propagated throughout the service provider’s network.
To emulate a point-to-point topology between two customer switches at different
sites, such as A and B, you can enable protocol tunneling on edge switches 1 and
2 for PAgP (Port Aggregation Protocol), LACP or UDLD (UniDirectional Link
Detection).
Figure 135 L2PT Network Example
27.1.2.1 Layer 2 Protocol Tunneling Mode
Each port can have two layer 2 protocol tunneling modes, Access and Tunnel.
• The Access port is an ingress port on the service provider's edge device (1 or 2
in Figure 135 on page 252 ) and connected to a customer switch (A or B).
Incoming layer 2 protocol packets received on an access port are encapsulated
and forwarded to the tunnel ports.
• The Tunnel port is an egress port at the edge of the service provider's network
and connected to another service provider’s switch. Incoming encapsulated
layer 2 protocol packets received on a tunnel port are decapsulated and sent to
an access port.
1
2
A
B
Service Provider's
Network
C
D
STP
STP
STP