Holddown

Holddown works by having each router start a timer when it first receive information about a network that is unreachable.

It can resolve situations where multiple routers are connected indirectly.

[1] In other words, a holddown prevents a router from receiving route updates until the network appears to be stable—until either an interface stops changing state (flapping) or a better route is learned.

If the router detects that a network is unreachable, the timer is started.

The router will then wait a preset number of seconds until the network stabilizes.