BGP - Delay Route Advertisments - Wait for KRT Drain

The router delays a BGP route advertisement in the forwarding information base (FIB) until the associated forwarding state is enabled in the forwarding table. The device only checks whether a more specific BGP prefix is installed in the FIB. But, in case of aggregates/summaries, it waits for KRT-queue to drain. The device does not wait for KRT-queue drain for all routes to avoid delaying control plane convergence. In some scenarios this might be problematic, because the more specific BGP prefix might be installed in the FIB but pointing to a pre-failure backup path. After a failure event, Packet Forwarding Engines are slow in installing the route change. Thus, attracting traffic toward such a router prematurely causes traffic loops. In essence, the behavior with enabled delayed BGP route advertisement is to avoid null routes but not a loop. To avoid such a situation, this feature enhances the delayed BGP route advertisement feature with an additional option, causing the device to always wait for KRT-queue to drain before advertising prefixes to peers. Using this option ensures that the more specific BGP routes' re-advertisement will also wait for KRT-queue to drain.