1. update from a neighbor - previously accessible network is now no longer accessible.
2. network marked as possibly down and starts the holddown timer.
3. If an update with a better metric for that network is received from any neighboring router
during the holddown period, the network is reinstated and the holddown timer is removed.
4. If an update from any other neighbor is received during the holddown period with the same
or worse metric for that network, that update is ignored. Thus, more time is allowed for the
information about the change to be propagated.
5. Routers still forward packets to destination networks that are marked as possibly down.
This allows the router to overcome any issues associated with intermittent connectivity. If the
destination network truly is unavailable and the packets are forwarded, black hole routing is
created and lasts until the holddown timer expires.