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Example: Configuring the MAC Address of an IRB Interface

This example shows how to configure the media access control (MAC) address of an integrated routing and bridging (IRB) interface for devices with Modular Port Concentrator (MPC) cards . An IRB interface is a Layer 3 routing interface that is used in a bridge domain or virtual private LAN service (VPLS) routing.


This example requires the following hardware and software components:

  • MX Series routers with MPC cards.

  • Junos OS Release 13.2 or later running on all devices.


Junos OS Release 13.2 and later support the assignment of MAC addresses to IRB logical interfaces. The IRB logical interfaces provide support for simultaneous Layer 2 bridging and Layer 3 routing within the same bridge domain. Packets that arrive on an interface of the bridge domain are either switched or routed, based on the destination MAC address of the packet. The packets with the router’s Layer 2 virtual MAC address, which is manually configured, are switched to Layer 2 interfaces.

Configuring a MAC address of an IRB logical interface allows the use of a transparent firewall between two VLANs on the same switch. When both VLANs are on the same subnet and traffic from one VLAN needs to go through the firewall to the host on the other VLAN, then the VLAN tag is changed to communicate with the host on the other VLAN.

Before the introduction of this feature, if the MAC address of an IRB logical interface was the same for both VLANs, the firewall dropped the traffic. This new feature allows you to configure distinct MAC addresses for different VLANs, which facilitates the exchange of traffic between two VLANs on the same switch.

In case of VPLS multihoming, if there is a failover of the primary provider edge (PE) router to a secondary PE router, the MAC address of an IRB changes. The hosts connected to the customer edge (CE) router must change their Address Resolution Protocol (ARP) for IRB’s IP and MAC address. This feature allows you to configure the same MAC address for IRB interfaces in both the primary and secondary PE routers and eliminates the need for changing the ARP binding of the IRB logical interface in CE routers, in case of a failover.

Figure 1 shows the sample topology.


Figure 1: Configuring the MAC Address of an IRB InterfaceConfiguring the MAC Address of an IRB Interface

In this example you configure MAC address of IRB logical interfaces.


CLI Quick Configuration

To quickly configure this example, copy the following commands, paste them into a text file, remove any line breaks, change any details necessary to match your network configuration, and then copy and paste the commands into the CLI at the [edit] hierarchy level.

Router R0

Router R1

Router R2

Configuring the MAC Address of an IRB Interface

Step-by-Step Procedure

The following example requires that you navigate various levels in the configuration hierarchy. For information about navigating the CLI, see Using the CLI Editor in Configuration Mode in the CLI User Guide.


Repeat this procedure for Juniper Networks Routers R1 and R2, modifying the appropriate interface names, addresses, and any other parameters for each router.

To configure the MAC address of an IRB interface on Router R0:

  1. Configure the physical interfaces.

  2. Configure the IRB logical interface.

  3. Configure the RSVP protocol.

  4. Configure the MPLS protocol.

  5. Configure the BGP protocol.

  6. Configure the OSPF protocol.

  7. Configure the LDP protocol.

  8. Configure the autonomous system (AS) number.

  9. Configure the bridge domains.


From configuration mode, enter the show interfaces, show protocols and show bridge-domains, commands and confirm your configuration. If the output does not display the intended configuration, repeat the instructions in this example to correct the configuration.

If you are done configuring the devices, commit the configuration.


Confirm that the configuration is working properly.

Verifying the MAC Address of the IRB Interface


Verify that the specified MAC address is assigned to the IRB interface.


From operational mode, run the show interfaces irb command on the device.

user@host# show interfaces irb


The output shows the manually configured MAC address in the MAC field.


If you did not configure the MAC address for a logical interface, the output does not include this value. However, the device uses the MAC address of the physical interface during data transmission.