1. The network topology is as follows:
CE1------C router (CPE)-------AR29 (PE)----ISP Network-----C router (PE)---------CE2
2. The version of the AR29 is 5.20 ESS 1710. The AR29 connects to the CPE using the Layer 2 board, whose interface mode is Trunk. The L2VPN is configured respectively on the two PEs (AR29 and C router) in Martini mode.
3. After completing all relevant device configurations, the two CEs cannot be successfully pinged. In addition, the status of the VC on the AR29 is Down. Therefore, the L2VC tunnel between the AR29 and the C router cannot be established.
Change the interface type of the C router from Access to Trunk. Then the L2VC goes Up.
switchport trunk encapsulation dot1q
switchport trunk allowed vlan 2
switchport mode trunk
mls qos trust dscp
1. The check of the routing tables of the AR29 and C router finds nothing abnormal.
2. Check the LSP tunnel on the AR29. The label indicating the LSP establishment triggered by the loopback address of the C router cannot be found. Check the configuration of the C router. It is found that LDP is not enabled on the uplink interface of the C router connecting to the ISP. After LDP is enabled on this interface of the C router, the LSP tunnel is established between the AR29 and the C router, but the L2VC between the AR29 and the C router still cannot go Up.
3. Check the interface encapsulation modes of the two PEs connecting to CEs. It is found that the encapsulation modes are different.
Configuration of the C router:
switchport access vlan 2
switchport mode access----------------Access interface
mls qos trust dscp
no ip address
xconnect 10.72.11.56 100 encapsulation mpls
----------------The packets passing through this VLAN interface do not contain VLAN tags. According to the implementation mechanism of C, the encapsulation mode is VLAN.
Configuration of the AR29:
mpls l2vc 10.72.11.57 100
port link-mode bridge
description to Cisco_CPE
port link-type trunk----------------Trunk interface
port trunk permit vlan 1 to 2 515
#-------------------This is a Trunk interface. Packets sent through the VLAN interface are encapsulated with VLAN tag 2. According to the convention on the AR router, the encapsulation mode is VLAN. In this case, the VLAN tag of packets passing through the C router is different from the VLAN tag encapsulated here. Therefore, the two types of packets cannot be transmitted normally between the two ends of the L2VPN.