Junos and the MPLS L2 Circuit Configuration

In this blog post, we will delve into the MPLS L2 Circuit Configuration, a crucial topic for students preparing for the JNCIS-ENT certification. MPLS (Multiprotocol Label Switching) is a protocol-agnostic routing technique designed to speed up and shape traffic flows across enterprise and service provider networks.

MPLS L2 Circuit Overview

MPLS L2 circuits are a type of Virtual Private Network (VPN) that allows the transportation of Layer 2 packets over an MPLS backbone. This is particularly useful for service providers who want to offer "point-to-point" services to their customers.

MPLS L2 Circuit Configuration on Junos

Configuring MPLS L2 circuits on Junos involves several steps. Let's break down the process:

1. Enable MPLS on the interfaces

First, you need to enable MPLS on the interfaces that will be part of the MPLS network. Here's an example of how to do this:

set interfaces ge-0/0/0 unit 0 family mpls
set interfaces ge-0/0/1 unit 0 family mpls

2. Configure the IGP

Next, you need to configure the Interior Gateway Protocol (IGP) to distribute the MPLS labels. OSPF is commonly used for this purpose. Here's an example:

set protocols ospf area interface ge-0/0/0.0
set protocols ospf area interface ge-0/0/1.0

3. Enable LDP

After that, you need to enable Label Distribution Protocol (LDP) on the interfaces. This is done as follows:

set protocols ldp interface ge-0/0/0.0
set protocols ldp interface ge-0/0/1.0

4. Configure the L2 circuit

Finally, you can configure the L2 circuit. Here's an example:

set routing-instances CustA instance-type l2vpn
set routing-instances CustA interface ge-0/0/0.0
set routing-instances CustA protocols l2vpn neighbor interface ge-0/0/0.0 virtual-circuit-id 100

In this example, CustA is the name of the routing instance, is the IP address of the remote PE router, and 100 is the virtual circuit ID.


After configuring the MPLS L2 circuit, you can verify its operation using the show l2vpn connections command:

show l2vpn connections

This command will display the status of all L2VPN connections, including the MPLS L2 circuits.


MPLS L2 circuits are a powerful tool for service providers offering point-to-point services. Understanding how to configure and verify these circuits on Junos is a key skill for any network engineer studying for the JNCIS-ENT certification. Remember, practice is key when it comes to mastering these concepts. Happy studying!

© Ben Jacobson.RSS