I know this was posted 5 year's ago, but I was looking for an answer to this as well, because ESET blocks this automatically. For years I paid no attention to it kept it blocked, and it seems unblocking this is not necessary, also it can stay blocked with out interfering with network traffic at all. If you are a network manager then this should be unblocked as if you are trying to monitor packets of all devices from your device, so you can see exactly as DNS is intended for to see what websites are making communication to other devices, and IP's establishing communication from peoples activities on devices (DNS communications). In security aspect it is a bad idea to unblock it, for packet sniffing network monitoring it's ok, but it would be an issue if a malicious user gets on your network, and I don't advise having this open on public Wi-Fi because of threat actors everything should be locked up for security and privacy on public wifi as you DNS sink hole every bad IP website to 0.0.0.0.