When Information Is Distributed

Now you understand what information is flooded. But when is it flooded? In a network that doesn't use MPLS Traffic Engineering, the IGP floods information about a link in three cases:

  • When a link goes up or down

  • When a link's configuration is changed (when link cost is modified, for example)

  • When it's time to periodically reflood the router's IGP information

All sorts of timers are associated with these actions. They differ depending on which IGP you use.

However, MPLS Traffic Engineering adds another reason to flood information—when link bandwidth changes significantly.

As tunnels are set up and torn down across interfaces, the amount of available bandwidth on an interface changes in accordance with the reservations ...

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