I have an RB3011UiAS with firmware 6.45.9 and RouterOS 6.49.7

Ever since I had this device I've been wondering about the cause for the unit spamming all of my interfaces with DHCP Discover packets at about 1/s. I've finally figured out that this is how the 'detect internet' feature works - presumably it throws the DHCP request out an interface and waits for a device to honour it and hand it a valid IP and router. Once that's configured it can then probe to determine whether it can reach "well known" addresses on the Internet ...

Except that this behaviour isn't obvious if you didn't configure it and accepted the defaults. Worse, if you have a bridge containing a number of physical interfaces, the physical interfaces get two DHCP Discover packets per second - one for the bridge and the other for the physical NIC.

So anyway, I'd searched for 'DHCP spam' previously on this forum and come up blank, so I'm posting this in the hopes that it makes things more obvious for the next person.

Apart from what you're seeing, there are (rare but consistent) reports of other random issues caused by "detect internet" functionality. Sadly MT never cared to comment on any if issues neither MT ever explained in details what exactly is affected by this functionality.

So yes, it does seem that disabling this functionality in case of any of hard-to-explain problems is a smart choice. Perhaps the second most important thing to do after one goes beyond most basic MT device setup (the most important thing being avoiding to use QuickSet at all cost).