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    Understanding BGP Advertising Rules for Labeled and Unlabeled Routes with the Same AFI

    When BGP receives a route to a prefix with the same AFI in both labeled and unlabeled forms, only one of these routes can be selected as the best route. The action taken after the best route is selected depends on whether the best route is labeled or unlabeled, and on what SAFI was previously negotiated with peers other than the one from which it received the best route. Table 1 lists the advertising action taken for the best route, whether labeled or unlabeled.

    Table 1: Advertising Action Taken Following Best Route Selection

    Best Route

    SAFI Negotiated with Peer

    Action Taken

    Unlabeled

    SAFI 1 and SAFI 4 (unlabeled and labeled)

    Advertises unlabeled route.

    Unlabeled

    SAFI 1 (unlabeled)

    Advertises unlabeled route.

    Unlabeled

    SAFI 4 (labeled)

    Withdraws labeled route.

    Labeled

    SAFI 1 and SAFI 4 (unlabeled and labeled)

    Advertises labeled route.

    Labeled

    SAFI 1 (unlabeled)

    Withdraws unlabeled route.

    Labeled

    SAFI 4 (labeled)

    Advertises labeled route.

    BGP sends a route-refresh message for each SAFI that it has negotiated with a peer. For example, if a speaker has negotiated both SAFI 1 and SAFI 4 with a particular peer, then when you issue the clear ip bgp neighbor soft-in command, BGP sends two route-refresh messages to this neighbor, one for each SAFI.

    Published: 2014-08-18