What steps help stabilize BGP route selection when multiple upstream providers advertise the same prefix?

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What steps help stabilize BGP route selection when multiple upstream providers advertise the same prefix?

Asked on Oct 13, 2025

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To stabilize BGP route selection when multiple upstream providers advertise the same prefix, you can implement a series of best practices that influence path selection and ensure consistent routing behavior. These practices involve manipulating BGP attributes and implementing policies to prefer certain paths.

Access your BGP router's configuration interface (e.g., Cisco IOS, Juniper Junos).
Identify the BGP attributes such as Local Preference, AS Path, and MED that can be adjusted to influence route selection.
Set a higher Local Preference for the preferred provider to prioritize its routes over others.
Use AS Path Prepending on less preferred routes to make them less attractive.
Configure MED (Multi-Exit Discriminator) values if you have control over both ends of the BGP session to influence inbound traffic.
Implement route filtering and prefix lists to control which routes are accepted and advertised.
Monitor BGP sessions and route stability using logging and network monitoring tools to ensure the desired behavior is maintained.

Additional Comment:

Local Preference is a powerful attribute for influencing outbound traffic within an AS.
AS Path Prepending is commonly used to influence inbound traffic from external ASes.
MED is less commonly used due to its limited scope and reliance on mutual agreements.
Regularly review BGP configurations and policies to adapt to changing network conditions.
Ensure redundancy and failover mechanisms are in place to handle provider outages.

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What steps help stabilize BGP route selection when multiple upstream providers advertise the same prefix?

Asked on Oct 13, 2025

Answer

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