MPLS Layer 2 Circuit Configuration Overview

1. Determine all of the routers that you want to participate in the circuit, and then complete the initial configuration of their interfaces. See the Interfaces User Guide for Security Devices.
2. For all of the routers in the circuit configuration, update the interface configurations to enable participation in the Layer 2 circuit.
   1. On the interface communicating with the other provider edge (PE) router, specify MPLS and IPv4, and include the IP address. For the loopback interface, specify inet, and include the IP address. For IPv4, designate the loopback interface as primary so it can receive control packets. (Because it is always operational, the loopback interface is best able to perform the control function.)
   2. On the PE router interface facing the customer edge (CE) router, specify a circuit cross-connect (CCC) encapsulation type. The type of encapsulation depends on the interface type. For example, an Ethernet interface uses ethernet-ccc. (The encapsulation type determines how the packet is constructed for that interface.)
   3. On the CE router interface that faces the PE router, specify inet (for IPv4), and include the IP address. In addition, specify a routing protocol such as Open Shortest Path First (OSPF), which specifies the area and IP address of the router interface.

   See Configuring Interfaces for Layer 2 VPNs (CLI Procedure).

3. For all of the routers in the circuit configuration, configure the appropriate protocols.
   1. MPLS—For PE routers and provider routers, use MPLS to advertise the Layer 2 circuit interfaces that communicate with other PE routers and provider routers.
   2. BGP—For PE routers, configure a BGP session.
   3. IGP and a signaling protocol—For PE routers, configure a signaling protocol (either LDP or RSVP) to dynamically set up label-switched paths (LSPs) through the provider network. (LDP routes traffic using IGP metrics. RSVP has traffic engineering that lets you override IGP metrics as needed.) You must use LDP or RSVP between PE routers and provider routers, but cannot use them for interfaces between PE routers and CE routers.

      In addition, configure an IGP such as OSPF or static routes on the PE routers to enable exchanges of routing information between the PE routers and provider routers. Each PE router's loopback address must appear as a separate route. Do not configure any summarization of the PE router's loopback addresses at the area boundary. Configure the provider network to run OSPF or IS-IS as an IGP, as well as IBGP sessions through either a full mesh or route reflector.

      See Configuring an IGP and the LDP Signaling Protocol (CLI Procedure) and Configuring an IGP and the RSVP Signaling Protocol (CLI Procedure).

4. For all of the routers in the circuit configuration, configure routing options. The only required routing option for circuits is the autonomous system (AS) number. You must specify it on each router involved in the circuit. See Configuring Routing Options for MPLS VPNs (CLI Procedure).
5. For PE routers, configure Layer 2 circuits on the appropriate interfaces. See Configuring an MPLS Layer 2 Circuit (CLI Procedure).