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 93 lists the advertising action taken for the best route, whether labeled or unlabeled.

Table 93: 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.

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