Triggered updates add responsiveness to a reconverging internetwork. Holddown timers introduce a
certain amount of skepticism to reduce the acceptance of bad routing information.
If the distance to a destination increases (for example, the hop count increases from 2 to 4), the router sets
a holddown timer for that route. Until the timer expires, the router will not accept any new updates for the
route.
Obviously, a trade-off is involved here. The likelihood of bad routing information getting into a table is
reduced but at the expense of the reconvergence time. Like other timers, holddown timers must be set
with care. If the holddown period is too short, it will be ineffective, and if it is too long, normal routing
will be adversely affected.