We have a three-machine MongoDB replica set. If we turn mongod off on one of them, everything is fine with the rest of the replica set. However, if we suddenly turn off the network interface on one of the machines, all db.open commands take 15 seconds extra. MongoDB works normally from the console at the time. If we drop all mongod traffic with iptables, everything works normally. But turning the interface off will cause the problem.

This causes our load balancer to think all hosts are down (limit is 5 secs) thus blocking all traffic to our HA setup.