Configuring MPLS L2VPN 1429Once LDP establishes an LSP between the two PEs and the label exchange and thebinding to CE are finished, a VC is set up and ready to transfer Layer 2 data.To allow the exchange of VC labels between PEs, the Martini method extendedLDP by adding the forwarding equivalence class (FEC) type of VC FEC. Moreover,as the two PEs exchanging VC labels may not be connected directly, a remote LDPsession must be set up to transfer the VC FEC and VC labels.With Martini MPLS L2VPN, only PEs need to maintain a small amount of VC labelsand LSP mappings and no P device contains Layer 2 VPN information. Therefore, ithas high scalability. In addition, to add a new VC, you only need to configure aone-way VC for each of the PEs. Your configuration will not affect the operationof the network.The Martini method applies to scenarios with sparse Layer 2 connections, such asa scenario with a start topology.Kompella MPLS L2VPN Kompella MPLS L2VPN is different from Martini MPLS L2VPN in that it does notoperate on the connections between CEs directly. It organizes different VPNs inthe whole service provider network and encodes each CE in a VPN. For aconnection to be established between two CEs, you only need to perform thesetasks on the PEs:■ Configuring CE IDs of the local and remote CEs respectively■ Specifying the circuit ID that the local CE assigns to the connection, such as theVPI/VCI with ATM.Kompella MPLS L2VPN uses extended BGP as the signaling protocol to distributeVC labels. Its label block mode allows it to assign labels to multiple connections ata time.With Kompella MPLS L2VPN, you can specify a local CE range to indicate howmany CEs can be connected with a CE. Then, the system assigns a label block of asize equal to the CE range for the CE. In this way, you can reserve some labels forthe VPN for future use. This wastes some label resources in a short term, but canreduce the VPN deployment and configuration workload in the case of expansion.Imagine that an enterprise VPN contains 10 CEs and the number may increase to20 in future service expansion. In this case, you can set the CE range of each CE to20. Thus, when you need to add a CE to the VPN later, you only need to modifythe configurations of the PE to which the new CE is connected. No change isrequired for the other PEs. This makes VPN expansion extremely simple.Similar to MPLS L3VPN, Kompella MPLS L2VPN also uses VPN targets to identifyVPNs. This brings excellent VPN networking flexibility.In addition, Kompella MPLS L2VPN supports local connections and inter-providerVPN solutions.Configuring MPLSL2VPNYou can select any of the implementation methods for MPLS L2VPN as needed.However, no matter what method you select, you must complete these two tasks:■ Configuring MPLS basic capability
