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Example: Interconnecting a Layer 2 Circuit with a Layer 2 Circuit

 

This example provides a step-by-step procedure and commands for configuring and verifying a Layer 2 circuit to a Layer 2 circuit interconnection. It contains the following sections:

Requirements

This example uses the following hardware and software components:

  • Junos OS Release 9.3 or later

  • 2 MX Series routers

  • 2 M Series routers

  • 1 T Series router

  • 1 EX Series router

Overview and Topology

The physical topology of a Layer 2 circuit to Layer 2 circuit interconnection is shown in Figure 1

Figure 1: Physical Topology of a Layer 2 Circuit Terminating into a Layer 2 Circuit
Physical Topology
of a Layer 2 Circuit Terminating into a Layer 2 Circuit

The logical topology of a Layer 2 circuit to Layer 2 circuit interconnection is shown in Figure 2

Figure 2: Logical Topology of a Layer 2 Circuit Terminating into a Layer 2 Circuit
Logical Topology of
a Layer 2 Circuit Terminating into a Layer 2 Circuit

Configuration

Note

In any configuration session, it is good practice to verify periodically that the configuration can be committed using the commit check command.

In this example, the router being configured is identified using the following command prompts:

  • CE2 identifies the customer edge 2 (CE2) router

  • PE1 identifies the provider edge 1 (PE1) router

  • CE3 identifies the customer edge 3 (CE3) router

  • PE3 identifies the provider edge 3 (PE3) router

  • CE5 identifies the customer edge 5 (CE5) router

  • PE5 identifies the provider edge 5 (PE5) router

This example contains the following procedures:

Configuring PE Router Customer-facing and Loopback Interfaces

Step-by-Step Procedure

To begin building the interconnection, configure the interfaces on the PE routers. If your network contains provider (P) routers, configure the interfaces on the P routers also. This example shows the configuration for Router PE1 and Router PE5.

  1. On Router PE1, configure the ge-1/0/0 interface encapsulation. To configure the interface encapsulation, include the encapsulation statement and specify the ethernet-ccc option (vlan-ccc encapsulation is also supported). Configure the ge-1/0/0.0 logical interface family for circuit cross-connect functionality. To configure the logical interface family, include the family statement and specify the ccc option.
  2. On Router PE5, configure the ge-2/0/0 interface encapsulation. To configure the interface encapsulation, include the encapsulation statement and specify the ethernet-ccc option. Configure the ge-2/0/0.0 logical interface family for circuit cross-connect functionality. To configure the logical interface family, include the family statement and specify the ccc option
  3. On Router PE3, configure the logical loopback interface. The loopback interface is used to establish the targeted LDP sessions to Routers PE1 and PE5.

Configuring Core-facing Interfaces

Step-by-Step Procedure

This procedure describes how to configure the core-facing interfaces on the PE routers. This example does not include all the core-facing interfaces shown in the physical topology illustration. Enable the mpls and inet address families on the core-facing interfaces.

  1. On Router PE1, configure the xe-0/3/0 interface. Include the family statement and specify the inet address family. Include the address statement and specify 10.10.1.1/30 as the interface address. Include the family statement and specify the mpls address family.
  2. On Router PE3, configure the core-facing interfaces. Include the family statement and specify the inet address family. Include the address statement and specify the IPv4 addresses shown in the example as the interface addresses. Include the family statement and specify the mpls address family. In the example, the xe-0/0/0 interface is connected to the route reflector, the xe-0/1/0 interface is connected to Router PE5, the xe-0/2/0 interface is connected to Router PE2, and the xe-0/3/0 interface is connected to Router PE1.
  3. On Router PE5, configure the xe-0/1/0 interface. Include the family statement and specify the inet address family. Include the address statement and specify 10.10.6.2/30 as the interface address. Include the family statement and specify the mpls address family.

Configuring Protocols

Step-by-Step Procedure

This procedure describes how to configure the protocols used in this example. If your network contains P routers, configure the protocols on the P routers also.

Configure all of the PE routers and P routers with OSPF as the IGP protocol. Enable MPLS and LDP protocols on all of the interfaces except fxp.0.

  1. On Router PE1, enable OSPF as the IGP. Enable the MPLS and LDP protocols on all interfaces except fxp.0. LDP is used as the signaling protocol on Router PE1 for the Layer 2 circuit. The following configuration snippet shows the protocol configuration for Router PE1:
  2. Configure the PE and P routers with OSPF as the IGP. Enable the MPLS and LDP protocols on all interfaces except fxp.0. The following configuration snippet shows the protocol configuration for Router PE3:

Configuring the Layer 2 Circuits

Step-by-Step Procedure

This procedure describes how to configure the Layer 2 circuits.

Note

In this example the ignore-mtu-mismatch statement is required for the circuit to come up.

  1. On Router PE1, configure the Layer 2 circuit. Include the l2circuit statement. Include the neighbor statement and specify the loopback IPv4 address of Router PE3 as the neighbor. Include the interface statement and specify ge-1/0/0.0 as the logical interface that is participating in the Layer 2 circuit. Include the virtual-circuit-id statement and specify 100 as the identifier. Include the ignore-mtu-mismatch statement to allow a Layer 2 circuit to be established even though the maximum transmission unit (MTU) configured on the local PE router does not match the MTU configured on the remote PE router.
  2. On Router PE5, configure the Layer 2 circuit. Include the l2circuit statement. Include the neighbor statement and specify the loopback IPv4 address of Router PE3 as the neighbor. Include the interface statement and specify ge-2/0/0.0 as the logical interface that is participating in the Layer 2 circuit. Include the virtual-circuit-id statement and specify 200 as the identifier. Include the ignore-mtu-mismatch statement to allow a Layer 2 circuit to be established even though the MTU configured on the local PE router does not match the MTU configured on the remote PE router.
  3. On Router PE3, configure the Layer 2 circuit to Router PE1. Include the l2circuit statement. Include the neighbor statement and specify the loopback IPv4 address of Router PE1 as the neighbor. Include the interface statement and specify iw0.0 as the logical interworking interface that is participating in the Layer 2 circuit. Include the virtual-circuit-id statement and specify 100 as the identifier. Include the ignore-mtu-mismatch statement to allow a Layer 2 circuit to be established even though the MTU configured on the local PE router does not match the MTU configured on the remote PE router.

    On Router PE3, configure the Layer 2 circuit to Router PE5. Include the l2circuit statement. Include the neighbor statement and specify the loopback IPv4 address of Router PE5 as the neighbor. Include the interface statement and specify iw0.1 as the logical interworking interface that is participating in the Layer 2 circuit. Include the virtual-circuit-id statement and specify 200 as the identifier. Include the ignore-mtu-mismatch statement.

Interconnecting the Layer 2 Circuits

Step-by-Step Procedure

Router PE3 is the router that is stitching the Layer 2 circuits together using the interworking interface. The configuration of the peer unit interfaces is what makes the interconnection.

  1. On Router PE3, configure the iw0.0 interface. Include the encapsulation statement and specify the ethernet-ccc option. Include the peer-unit statement and specify the logical interface unit 1 as the peer tunnel interface.

    On Router PE3, configure the iw0.1 interface. Include the encapsulation statement and specify the ethernet-ccc option. Include the peer-unit statement and specify the logical interface unit 0 as the peer tunnel interface.

  2. On Router PE3, configure the Layer 2 interworking l2iw protocol. To configure the Layer 2 interworking protocol, include the l2iw statement at the [edit protocols] hierarchy level.
  3. On each router, commit the configuration.

Verifying the Layer 2 Circuit to Layer 2 Circuit Interconnection

Step-by-Step Procedure

Verify that the Layer 2 circuit connection on Router PE1 is up, the LDP neighbors are correct, and the MPLS label operations are correct.

  1. On Router PE1, use the show l2circuit connections command to verify that the Layer 2 circuit from Router PE1 to Router PE3 is Up.
    user@PE1> show l2circuit connections
  2. On Router PE1, use the show ldp neighbor command to verify that the IPv4 address of Router PE3 is shown as the LDP neighbor.
    user@PE1> show ldp neighbor
  3. On Router PE 1, use the show route table mpls.0 command to verify the Layer 2 circuit is using the LDP label to Router PE3 in both directions (Push and Pop). In the example below, the Layer 2 circuit is associated with LDP label 301328.
    user@PE1> show route table mpls.0
  4. On Router PE3, use the show l2circuit connections command to verify that the Layer 2 circuit from Router PE3 to Router PE5 is Up, that the Layer 2 circuit from Router PE3 to Router PE1 is Up, that the connections to Router PE1 and Router PE5 use the iw0 interface, and that the status for both local iw0 interfaces is Up.
    user@PE3> show l2circuit connections
  5. On Router PE3, use the show ldp neighbor command to verify that the correct IPv4 addresses are shown as the LDP neighbor.
    user@PE3> show ldp neighbor
  6. On Router PE3, use the show route table mpls.0 command to verify that the mpls.0 routing table is populated with the Layer 2 interworking routes. Notice that in this example, the router is swapping label 314736 received from Router PE1 on the iw0.0 to label 301328.
    user@PE3> show route table mpls.0
  7. Verify that Router CE1 can send traffic to and receive traffic from Router CE5 across the interconnection, using the ping command.
    user@CE1>ping 198.51.100.11
  8. Verify that Router CE5 can send traffic to and receive traffic from Router CE1 across the interconnection, using the ping command.
    user@CE5>ping 198.51.100.1

Results

The configuration and verification of this example has been completed. The following section is for your reference.

The relevant sample configuration for Router PE1 follows.

Router PE1

The relevant sample configuration for Router PE3 follows.

Router PE3