What type of routing table update message does IGRP use to quickly remove a route?

IGRP (Interior Gateway Routing Protocol) uses flash updates to quickly remove a route from its routing table. These updates are initiated when there is a significant change in the network, such as a route becoming unreachable. Flash updates are designed to expedite the process of notifying neighboring routers about such critical changes, therefore enhancing the overall responsiveness of the network.

The main advantage of flash updates is their ability to quickly propagate route changes without waiting for the next regular update cycle, which can help prevent routing loops and optimize network stability. In scenarios where speed is essential, such as during network disruptions, flash updates ensure that all routers remain synchronized with the most current routing information in a timely manner.

This mechanism contrasts sharply with other types of updates. Regular updates are sent at scheduled intervals, which may not provide timely information about urgent route changes. Triggered updates are responses to specific events, but they do not inherently emphasize rapid removal of routes in the same way flash updates do. Periodic updates follow a routine schedule and are less responsive to immediate changes in the network, thus they are not suitable for quick detections and removals.