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Configuring Integrated Routing and Bridging in ACX Series

Integrated routing and bridging (IRB) provides simultaneous support for Layer 2 bridging and Layer 3 routing on the same interface. IRB enables you to route packets to another routed interface or to another bridge domain that has an IRB interface configured. You configure a logical routing interface by including the irb statement at the [edit interfaces] hierarchy level and include that interface in the bridge domain. For more information about how to configure a routing interface, see the Junos OS Network Interfaces Library for Routing Devices.


You can include only one routing interface in a bridge domain.

The following are the list of features supported for IRB:

  • Family inet, inet6, and iso are supported on an IRB interface.

  • Routing protocols supported on an IRB interface are BGP, ISIS, OSPF, RIP, IGMP, and PIM.

  • DHCP Relay with option 82 is supported on an IRB interface.

  • IRB can be added in a VRF routing instance.

  • VRRP is supported on an IRB inteface.

  • Bidirectional Forwarding Detection (BFD) protocol is supported on an IRB interface.

  • The following Class-of-Service configurations are supported on an IRB interface:

    • The IRB classifiers and rewrite on routed packets.

    • Fixed classifier can be applied on an IRB logical interface.

    • Firewall filters (multifield filter) can be used to assign forwarding class and loss priority. You should define a family inet or inet6 filter and apply it as the input filter on an IRB logical interface under family inet.


      physical-interface-filter is not supported for family inet6 filter on IRB logical interface.

    • Re-write can be applied only at the IRB interface level.

    • dscp, inet-precedence, ieee-802.1, and ieee-802.1ad values can be rewritten.

ACX routers do not support MPLS families on IRB.

IRB can be configured under the following hierarchies:

  • [edit intefaces irb interface_type] hierarchy level

    • disable—Disables the interface

    • gratuitous-arp-reply—Enables gratuitous ARP reply

    • hold-time—Hold time for link up and link down

    • mtu—Maximum transmit packet size (256..9192)

    • no-gratuitous-arp-reply—Does not enable gratuitous ARP reply

    • no-gratuitous-arp-request—Ignores gratuitous ARP request

  • [edit interfaces irb.unit family (inet | inet6 | iso)] hierarchy level

  • [edit bridge-domains routing-interface interface irb.unit] hierarchy level

  • [edit routing-instances instance-type vrf] hierarchy level

  • [edit protocols (bgp | isis | ospf | rip | igmp | pim) interface irb.unit] hierarchy level

  • [edit class-of-service interfaces irb]] hierarchy level

In ACX5048 and ACX5096 routers, you can configure IRB at the [edit vlans vlan-name] l3-interface irb.unit; level.


The Layer 2 CLI configurations and show commands for ACX5048 and ACX5096 routers differ compared to other ACX Series routers. For more information, see Layer 2 Next Generation Mode for ACX Series.

To configure a bridge domain with IRB support, include the following statements:

For each bridge domain that you configure, specify a bridge-domain-name. You must also specify the value bridge for the domain-type statement.

For the vlan-id statement, you can specify either a valid VLAN identifier or the none option.

The vlan-tags statement enables you to specify a pair of VLAN identifiers; an outer tag and an inner tag.


For a single bridge domain, you can include either the vlan-id statement or the vlan-tags statement, but not both.

To include one or more logical interfaces in the bridge domain, specify the interface-name for each Ethernet interface to include that you configured at the [edit interfaces] hierarchy level.


A maximum of 4000 active logical interfaces are supported on a bridge domain configured for Layer 2 bridging.

To associate a routing interface with a bridge domain, include the routing-interface routing-interface-name statement and specify a routing-interface-name you configured at the [edit interfaces irb] hierarchy level. You can configure only one routing interface for each bridge domain. For more information about how to configure logical and routing interfaces, see the Junos OS Network Interfaces Library for Routing Devices.

In Junos OS Release 9.0 and later, IRB interfaces are supported for multicast snooping. For more information about multicast snooping, see the Junos OS Multicast Protocols User Guide.


When you configure multiple IRB logical interfaces, all the IRB logical interfaces share the same MAC address.

The following is a sample configuration for IRB over bridge domain: