Why is the Internet lost?

Question

Computer networks

There is a mikrotik sxt lte that acts as a gateway to the Internet.
Raises 4G Internet, gives it to the domain network.
Mikrotik is configured a bit primitively, i.e. no fancy firewall rules, no QoS. Almost like a QuickSet.

Until recently, everything worked like clockwork, there were no complaints.

From a couple of months ago, the Internet began to disappear on some computers, i.e. it just doesn't exist is all. Tracing on problem computers breaks on the gateway. More precisely, the gateway simply does not respond. At the same time, the Internet can work perfectly on a nearby computer. The problem appears suddenly, just as suddenly goes away.

Computers in a Windows domain, the domain is for single sign-on only, there are no restrictions.

The network is on unmanaged switches, rebooting them does not help. Tried changing mac addresses to no avail. Did not change only the adapters themselves.

While we are trying to get out with an additional gateway, but this is wrong, we need to understand what is interfering in the network.

Answer 1

Very similar to IP address conflict
- set a small lease time for 10-15 minutes on the dchp server
- install arpwatch (linux) or arp monitor (Windows) and watch
- preferably managed switches with dhcp- and igmp-snooping
MAC change - very bad idea ...
Well, I would like to look at the network itself. How much where and what...

Answer 2

look at ipconfig / all on problem computers and compare with workers