Cisco 3845 Software Guide - Page 249

Chapter 11 Configuring Ethernet Virtual Connections (EVCs) Configuring Other Features on EFPs Figure 11-4 Layer 2 Network Topology without Proper Convergence Customer X virtual network VLANs 1 to 100 101821 OL-23400-01 In a service-provider network, you can use Layer 2 protocol tunneling to enhance the creation of EtherChannels by emulating a point-to-point network topology. When you enable protocol tunneling (PAgP or LACP) on the service-provider switch, remote customer switches receive the PDUs and can negotiate the automatic creation of EtherChannels. For example, in Figure 11-5, Customer A has two switches in the same VLAN that are connected through the SP network. When the network tunnels PDUs, switches on the far ends of the network can negotiate the automatic creation of EtherChannels without needing dedicated lines. Figure 11-5 Layer 2 Protocol Tunneling for EtherChannels EtherChannel 1 Customer A Site 1 VLAN 17 Service Provider VLAN 18 Switch A Switch C VLAN 19 VLAN 20 Switch B Switch D VLAN 17 VLAN 18 VLAN 19 VLAN 20 EtherChannel 1 Customer A Site 2 101844 Trunk Asymmetric link Use the l2protocol tunnel protocol service-instance configuration command to enable Layer 2 protocol tunneling on a service instance: Valid protocols include CDP, DTP, LACP, LLDP, PAgP, STP, VTP, and UDLD. If a protocol is not specified for a service instance, the protocol frame is dropped at the interface. This is an example of Layer 2 protocol tunneling configuration: Switch (config)# interface gigabitethernet0/2 Switch (config)# switchport mode trunk Switch (config)# switchport trunk allowed vlan none Switch (config-if)# service instance 10 Ethernet Switch (config-if-srv)# encapsulation untagged, dot1q 200 second-dot1q 300 Cisco ME 3800X and 3600X Switch Software Configuration Guide 11-23