Need to add DCs to host file

Question

Hello,
My servers (Windows Server 2016 and 2019) are hosted on a private cloud, that I don't manage.
There are multiple VLANs: DCs are not on the same VLAN as servers.
Servers are joined to the domain and are showing from time to time, several time a day error 0XC000005E – “There are currently no logon servers available to service the logon request.” and EventID 5719, NETLOGON - "This computer was not able to set up a secure session with a domain controller". During this, DNS resolution stops.
If I add DCs to the hosts file of each server, errors almost disappear and we are able to use RDP, SQL, ISS, shared folder without issues.
Team in charge of the private cloud tells me there is no issue on domain side, neither on network side.
I highly doubt it :)

Time synchronization is good.
Network card are manually configured and have been checked.
Is there anything i can test to pin point the issue (I've already send a lot of log extract showing 0XC000005E or EventID 5719 errors)?
Thanks,
Steph

Answer 1

I'd confirm the VPN connectivity is good, also check the required ports are flowing between networks.
https://learn.microsoft.com/en-us/troubleshoot/windows-server/identity/config-firewall-for-ad-domains-and-trusts#windows-server-2008-and-later-versions
https://www.microsoft.com/en-us/download/details.aspx?id=24009

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