Configuring VLAN Identifiers for a Bridge Domain or a VPLS Routing Instance

You can configure VLAN identifiers for a bridge domain or a VPLS routing instance in the following ways:

• 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 Network Interfaces Configuration Guide.
• 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.

The vlan-id and vlan-tags statements are used to specify the normalizing VLAN identifier under the bridge domain or VPLS routing instance. The normalizing VLAN identifier is used to perform the following functions:

• 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] or [edit logical-systems logical-system-name interfaces interface-name] 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] or [edit logical-systems logical-system-name interfaces interface-name] 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 VPNs Configuration Guide.

Note: For a single bridge domain or VPLS routing instance, you can configure either the vlan-id statement or the vlan-tags statement, but not both.

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 7. 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 8.

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.

The vlan-id all statement enables you to configure bridging for several VLANs with a minimum amount of configuration. Configuring this statement creates a learning domain for:

• 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

The following steps outline the process for bridging a packet received over a Layer 2 logical interface when you specify a normalizing VLAN identifier using either the vlan-id number or vlan-tags statement for a bridge domain or a VPLS routing instance:

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 7.
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 8.

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 7 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 7: Statement Usage and Input Rewrite Operations for VLAN Identifiers for a Bridge Domain

Table 8 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.

Table 8: Statement Usage and Output Rewrite Operations for VLAN Identifiers for a Bridge Domain

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