Technical Documentation

Configuring a Bridge Domain

A bridge domain must include a set of logical interfaces that participate in Layer 2 learning and forwarding. You can optionally configure a VLAN identifier and a routing interface for the bridge domain to also support Layer 3 IP routing.

To enable a bridge domain, include the following statements:

[edit]bridge-domains {bridge-domain-name {domain-type bridge:interface interface-name;routing-interface routing-interface-name;vlan-id (none | all | number);vlan-id-list [ vlan-id-numbers ];vlan-tags outer number inner number);}}protocols {mstp {...mstp-configuration ...}}

For the vlan-id statement, you can specify either a valid VLAN identifier or the none or all options. For information about VLAN identifiers and VLAN tags for a bridge domain, see Guidelines for Configuring VLAN Identifiers for Bridge Domains and VPLS Routing Instances and Configuring VLAN Identifiers for Bridge Domains and VPLS Routing Instances.

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

Note: A maximum of 4000 active logical interfaces are supported on a bridge domain or on each mesh group in a virtual private LAN service (VPLS) instance configured for Layer 2 bridging.

By default, each bridge domain maintains a Layer 2 forwarding database that contains media access control (MAC) addresses learned from packets received on the ports that belong to the bridge domain. You can modify Layer 2 forwarding properties, including disabling MAC learning for the entire system or a bridge domain, adding static MAC addresses for specific logical interfaces, and limiting the number of MAC addresses learned by the entire system, the bridge domain, or a logical interface.

You can also configure spanning tree protocols to prevent forwarding loops. For more information, see Spanning-Tree Protocols Supported on MX Series Routers.

In JUNOS Release 8.5 and later, you can configure IGMP snooping for a bridge domain. For more information, see the Junos Multicast Protocols Configuration Guide.


Published: 2010-05-11