1. RIP router enters holddown when the existing route in the routing table is unreachbale, & it receives an advertisement for same dest with higher metric. During the holdtime period if it doesnt recv any advertisement with lower metric, then rip accepts the route with higher metric & updates the table after holddown time expires.
2. However if a low metric route comes at time of holdtime, rip will accept the route & update the neighbors without waiting for the holddown timer to expire.
3. If a lower metric route is live, & rip recv a high metric route then it'll straight away reject the higher metric & continue to adv the lower metric route & thus no effect on traffic. But if the route is not reachable then traffic is not forwarded till it populates the table with new or better route.