Cisco 4500M

19-8
Software Configuration Guide—Release 12.2(25)EW
OL-6696-01
Chapter 19 Configuring 802.1Q and Layer 2 Protocol Tunneling
Understanding Layer 2 Protocol Tunneling
Customer A’s Site 1 will build a spanning tree on the switches at that site without considering
convergence parameters based on Customer A’s switch in Site 2. Figure 19-5 shows one possible
spanning tree topology.
Figure 19-4 Layer 2 Protocol Tunneling
Figure 19-5 Layer 2 Network Topology without Proper Convergence
Customer A Site 2
VLANs 1 to 100
Customer B Site 2
VLANs 1 to 200
Customer B Site 1
VLANs 1 to 200
Customer A Site 1
VLANs 1 to 100
VLAN 30
Trunk
ports
Switch 1
Switch 1
Trunk
ports
VLAN 30
VLAN 40
Service
provider
74073
Trunk
Asymmetric link
VLAN 30
VLAN 40
Trunk
ports
Switch 2
Switch 3
Switch 4
Trunk
ports
74017
Customer A
virtual network
VLANs 1 to 100