How to set up stable access to network resources behind Mikrotik VPN?

Question

VPN

Greetings!
There is such a problem: in the central and remote offices there were old dead Zuksels as gateways. It was decided to replace them with 951 Mikrotiks.
At the central office there is a server group with a file share. AD, 1c with SQL. It was required to connect a remote office via VPN to access network resources.
I set up an L2TP server at the central office on Mikrotik without ipsec. At the remote office, microt was configured to connect to this server.
Both microtas are tuned plus or minus the same. Access to the Internet, DHCP server to your subnet, routes to the neighboring grid.
At first, both grids rustled normally. A day later, the office started having problems loading pages (the "host definition" hangs for a few seconds when opening pages), and in the remote office, users' access to network resources and disks randomly falls off. Enabling disabling the interface in Windows for a while solves the problem, but then this crap is repeated.
I searched many forums and didn't find anything similar.
Maybe someone faced a similar problem? Or at least offer an option where to dig.

Answer 1

On a fresh head in the morning I sat down to understand.
I found a running DHCP server on one of the servers, made by some other previous admin. Apparently he got along with the zuksels, because dhcp was launched on each zuksel. Disabling this server seems to have solved both problems. Computers on the remote network started to go to the main network normally, page loading works as it should.
Thanks to all!

Answer 2

Dig towards IP-Firewall-Filter Rules
You can try to play around with MTU values ​​on L2tp interfaces

Answer 3

And you are brave, drive a ton of traffic in the tunnel.
Z.Y. nobody does that. need to work with balls? RDP.

Answer 4

A picture is worth hundreds of words!
What does the Windows interface have to do with the tunnel?
What is the routing logic/scheme? Default gate for Mikrotiks - two? Does everyone have their own?
What happens on Mikrotik in terms of CPU/RAM/traffic/number of sessions?
What happens to ping from office networks to the Internet and to the external IP of the opposite office?
What about pinging both external IPs from the internet?