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    VLANs Within a Bridge Domain or VPLS Instance

    A packet received on a physical port is only accepted for processing if the VLAN tags of the received packet match the VLAN tags associated with one of the logical interfaces configured on the physical port. The VLAN tags of the received packet are translated only if they are different than the normalized VLAN tags. For the translation case, the VLAN identifier tags specify the normalized VLAN. For this case, the terms “learn VLAN” and “normalized VLAN” can be used interchangeably.

    You can specify the normalized VLAN using one of the following conditions:

    • The VLAN identifier is determined explicitly by configuration
    • The VLAN identifier is specified as “none,” meaning the VLAN tags are not translated or generated
    • The inner and outer VLAN identifier tags are both determined explicitly by configuration

    Frames with VLAN identifier tags configured might have their inner or outer VLAN identifiers checked at egress. However, the exact circumstances of the VLAN check vary with configuration parameters.

    In particular, for a routing instance or bridge domain with the vlan-id all statement configured, then the VLAN check is enabled only in following conditions.

    • If the routing instance or bridge domain has the vlan-id all statement configured and there is a discrete outer VLAN identifier configured (that is, the logical interface is single tagged), then the VLAN check is enabled for the outer VLAN identifier.
    • If the routing instance or bridge domain has the vlan-id all statement configured and the inner VLAN identifier is a range, then the VLAN check is enabled for the inner VLAN identifier range.
    • If the routing instance or bridge domain has the vlan-id all statement configured and the outer VLAN identifier is a range, then the VLAN check is enabled for the outer VLAN identifier range.
    • If the routing instance or bridge domain has the vlan-id all statement configured and there is a discrete inner VLAN identifier (that is, the logical interface is dual-tagged), then the VLAN check is enabled for the inner VLAN identifier value.

    These conditions and results are shown in Table 1.

    Table 1: VLAN Checking Based on Inner and Outer VLAN Identifier Configuration.

    Outer VLAN Identifier

    Inner VLAN Identifier

    VLAN Identifier Checked

    Discrete

    (None)

    Outer

    Range

    Inner

    Range

    Outer

    Discrete

    Discrete

    Inner

    Note: If there is no VLAN configured on the routing instance or bridge domain, then neither the inner VLAN identifier nor the outer VLAN identifier on frames are checked at egress. This is consistent with other behavior and the expected one.

    Modified: 2017-10-26