What factors cause slow convergence during BGP graceful restart events?

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What factors cause slow convergence during BGP graceful restart events?

Asked on Nov 15, 2025

Answer

BGP graceful restart events can experience slow convergence due to several factors, including the time taken for routers to re-establish adjacencies and exchange routing information. This process is influenced by the configured timers, the size of the routing table, and the network topology. Understanding these factors helps in optimizing BGP configurations for faster convergence.

Example Concept: During a BGP graceful restart, routers temporarily retain forwarding state while adjacencies are re-established. Factors such as the "Restart Time" and "Stale Timer" settings, the number of prefixes exchanged, and the complexity of the network topology can affect convergence speed. Properly tuning these parameters and ensuring efficient routing policies can mitigate delays.

Additional Comment:

Ensure "Restart Time" and "Stale Timer" are appropriately configured to balance between convergence speed and stability.
Monitor the size of the routing table; larger tables can increase convergence time.
Consider network topology complexity, as more interconnected paths may require additional time for full convergence.
Regularly review and optimize BGP policies to reduce unnecessary path calculations.

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