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Route flapping

Route flapping

Route flapping definition

Route flapping is an issue that occurs in computer networking and telecommunications and refers to a router continuously fluctuating in a short time period while it is routing traffic.

More specifically, router flapping includes the router constantly switching between being available and unavailable and displaying significant changes in router metrics. Additionally, in most cases, users can detect route flapping because their router constantly updates and withdraws network prefixes, meaning it alternatively advertises the two best destinations.

Of course, route flapping is common and usually cannot be avoided. However, when it happens often and at a higher intensity, it distorts the routing topology, making it hard for the devices that send traffic to figure out the next route hop. This, in turn, can cause your network to experience latency or downtime.

Also, because the traffic cannot be sent to the correct destination, it can be re-routed to other devices, creating routing loops and further complicating the issue.

See also: load balancing router, low latency

Common causes of route flapping

  • Using dynamic routing.
  • Misconfiguring the load balancing between paths and hops.
  • Hardware and software failures.
  • Broken connections or errors in communication links.

Two methods for preventing route flapping

  • Route dampening, which includes suppressing flapping routes and stopping them from being advertised.
  • Route summarization, which involves limiting the visibility of the router’s topology so that the router is not affected by topology changes.

Further reading

Ultimate digital security