Cisco 3845 - Security Bundle Router Software Manual page 248

Configuring Other Features on EFPs
configured protocols cross the service-provider network and are delivered to customer switches on the
outbound side of the service-provider network. Identical packets are received by all customer ports on
the same VLANs with these results:
Users on each of a customer's sites can properly run STP, and every VLAN can build a correct
•
spanning tree based on parameters from all sites and not just from the local site.
• CDP discovers and shows information about the other Cisco devices connected through the
service-provider network.
• VTP provides consistent VLAN configuration throughout the customer network, propagating to all
switches through the service provider that support VTP.
Customers use Layer 2 protocol tunneling to tunnel BPDUs through a service-provider network without
interfering with internal provider network BPDUs.
On ME 3800X and ME 3600X switches, Layer 2 protocol tunneling is supported on EFPs, but not on
Note
switchports.
In Figure
service-provider network. If the network does not tunnel PDUs, switches on the far ends of the network
cannot properly run STP, CDP, and other Layer 2 protocols. For example, STP for a VLAN on a switch
in Customer X, Site 1, will build a spanning tree on the switches at that site without considering
convergence parameters based on Customer X's switch in Site 2. This could result in the topology shown
in Figure
Figure 11-3
Cisco ME 3800X and 3600X Switch Software Configuration Guide
11-22
11-3, Customer X has four switches in the same VLAN, which are connected through the
11-4.
Layer 2 Protocol Tunneling
Customer X Site 1
VLANs 1 to 100
VLAN 30
VLAN 30
Switch A
Switch B
VLAN 40
Customer Y Site 1
VLANs 1 to 200
Chapter 11 Configuring Ethernet Virtual Connections (EVCs)
Service
provider
Trunk
Trunk
ports
ports
Trunk
Trunk
ports
ports
Trunk
Asymmetric link
Customer X Site 2
VLANs 1 to 100
VLAN 30
Switch C
Switch D
VLAN 40
Customer Y Site 2
VLANs 1 to 200
OL-23400-01