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Configuring VLAN Identifiers for Bridge Domains and VPLS Routing Instances

• By using the input-vlan-map and the output-vlan-map statements at the [edit interfaces interface-name] or [edit logical-systems logical-system-name interfaces interface-name] hierarchy level to configure VLAN mapping. For information about configuring input and output VLAN maps to stack and rewrite VLAN tags in incoming or outgoing frames, see the Junos OS Network Interfaces Library for Routing Devices.
• By using either the vlan-id statement or the vlan-tags statement to configure a normalizing VLAN identifier. This topic describes how normalizing VLAN identifiers are processed and translated in a bridge domain or a VPLS routing instance.

• Translate, or normalize, the VLAN tags of received packets received into a learn VLAN identifier.
• Create multiple learning domains that each contain a learn VLAN identifier. A learning domain is a MAC address database to which MAC addresses are added based on the learn VLAN identifier.

Note: You cannot configure VLAN mapping using the input-vlan-map and output-vlan-map statements if you configure a normalizing VLAN identifier for a bridge domain or VPLS routing instance using the vlan-id or vlan-tags statements.

To configure a VLAN identifier for a bridge domain, include either the vlan-id or the vlan-tags statement at the [edit interfaces interface-name unit logic-unit-number family bridge] or [edit logical-systems logical-system-name interfaces interface-name unit logic-unit-number family bridge] hierarchy level, and then include that logical interface in the bridge domain configuration. For more information about configuring a bridge domain, see Configuring a Bridge Domain.

For a VPLS routing instance, include either the vlan-id or vlan-tags statement at the [edit interfaces interface-name unit logic-unit-number] or [edit logical-systems logical-system-name interfaces interface-name unit logic-unit-number] hierarchy level, and then include that logical interface in the VPLS routing instance configuration. For more information about configuring a VPLS routing instance, see the Junos OS VPNs Library for Routing Devices.

Note: The maximum number of Layer 2 interfaces that you can associate with a bridge domain or a VPLS instance on MX Series routers is 4000.

Note: For a single bridge domain or VPLS routing instance, you can include either the vlan-id or the vlan-tags statement, but not both. If you do not configure a vlan-id, vlan-tags, or vlan-id-list [ vlan-id-numbers ] for the bridge domain or the VPLS routing instance, the Layer 2 packets received are forwarded to the outbound Layer 2 interface without having the VLAN tag modified unless an output-vlan-map is configured on the Layer 2 interface. This results in a frame being forwarded to a Layer 2 interface with a VLAN tag that is different from what is configured for the Layer 2 interface. Note that a frame received from the Layer 2 interface is still required to match the VLAN tag(s) specified in the interface configuration. The invalid configuration may cause a Layer 2 loop to occur.

The VLAN tags associated with the inbound logical interface are compared with the normalizing VLAN identifier. If the tags are different, they are rewritten as described in Table 1. The source MAC address of a received packet is learned based on the normalizing VLAN identifier.

Note: You do not have to specify a VLAN identifier for a bridge domain that is performing Layer 2 switching only. To support Layer 3 IP routing, you must specify either a VLAN identifier or a pair of VLAN tags. However, you cannot specify the same VLAN identifier for more than one bridge domain within a routing instance. Each bridge domain must have a unique VLAN identifier.

If the VLAN tags associated with the outbound logical interface and the normalizing VLAN identifier are different, the normalizing VLAN identifier is rewritten to match the VLAN tags of the outbound logical interface, as described in Table 2.

For the packets sent over the VPLS routing instance to be tagged by the normalizing VLAN identifier, include one of the following configuration statements:

• vlan-id number to tag all packets that are sent over the VPLS virtual tunnel (VT) interfaces with the VLAN identifier.
• vlan-tags outer number inner number to tag all packets sent over the VPLS VT interfaces with dual outer and inner VLAN tags.

Use the vlan-id none statement to have the VLAN tags removed from packets associated with an inbound logical interface when those packets are sent over VPLS VT interfaces. Note that those packets might still be sent with other customer VLAN tags.

• Each inner VLAN, or learn VLAN, identifier of a logical interface configured with two VLAN tags
• Each VLAN, or learn VLAN, identifier of a logical interface configured with one VLAN tag

We recommend that you do not use customer VLAN IDs in a VPLS routing instance because customer VLAN IDs are used for learning only.

Note: If you configure the vlan-id all statement in a VPLS routing instance, we recommend using the input-vlan-map pop and output-vlan-map push statements on the logical interface to pop the service VLAN ID on input and push the service VLAN ID on output and in this way limit the impact of doubly-tagged frames on scaling. You cannot use the native vlan- id statement when the vlan-id all statement is included in the configuration.

• Each VLAN listed: vlan-id-list [ 100 200 300 ]
• Each VLAN in a range: vlan-id-list [ 100-200 ]
• Each VLAN in a list and range combination: vlan-id-list [ 50, 100-200, 300 ]

1. When a packet is received on a physical port, it is accepted only if the VLAN identifier of the packet matches the VLAN identifier of one of the logical interfaces configured on that port.
2. The VLAN tags of the received packet are then compared with the normalizing VLAN identifier. If the VLAN tags of the packet are different from the normalizing VLAN identifier, the VLAN tags are rewritten as described in Table 1.
3. If the source MAC address of the received packet is not present in the source MAC table, it is learned based on the normalizing VLAN identifier.
4. The packet is then forwarded toward one or more outbound Layer 2 logical interfaces based on the destination MAC address. A packet with a known unicast destination MAC address is forwarded only to one outbound logical interface. For each outbound Layer 2 logical interface, the normalizing VLAN identifier configured for the bridge domain or VPLS routing instance is compared with the VLAN tags configured on that logical interface. If the VLAN tags associated with an outbound logical interface do not match the normalizing VLAN identifier configured for the bridge domain or VPLS routing instance, the VLAN tags are rewritten as described in Table 2.

The tables below show how VLAN tags are applied for traffic sent to and from the bridge domain, depending on how the vlan-id and vlan-tags statements are configured for the bridge domain and on how VLAN identifiers are configured for the logical interfaces in a bridge domain or VPLS routing instance. Depending on your configuration, the following rewrite operations are performed on VLAN tags:

• pop—Remove a VLAN tag from the top of the VLAN tag stack.
• pop-pop—Remove both the outer and inner VLAN tags of the frame.
• pop-swap—Remove the outer VLAN tag of the frame and replace the inner VLAN tag of the frame.
• swap—Replace the VLAN tag of the frame.
• push—Add a new VLAN tag to the top of the VLAN stack.
• push-push—Push two VLAN tags in front of the frame.
• swap-push—Replace the VLAN tag of the frame and add a new VLAN tag to the top of the VLAN stack.
• swap-swap—Replace both the outer and inner VLAN tags of the frame.

Table 1 shows specific examples of how the VLAN tags for packets sent to the bridge domain are processed and translated, depending on your configuration. “–” means that the statement is not supported for the specified logical interface VLAN identifier. “No operation” means that the VLAN tags of the received packet are not translated for the specified input logical interface.

Table 2 shows specific examples of how the VLAN tags for packets sent from the bridge domain are processed and translated, depending on your configuration. “–” means that the statement is not supported for the specified logical interface VLAN identifier. “No operation” means that the VLAN tags of the outbound packet are not translated for the specified output logical interface.