DNS option sets problem

This is more about how Windows handles machine discovery in a workgroup environment which then leads us back to what you've already identified which is: Windows uses DNS to find other machines and therefore naming is important.

Outside of AWS you'd normally run the Windows DNS service; you can still do that but it then makes it more difficult (not impossible!) to resolve VPC, AWS and Internet-based resources. You could also set up a Windows Active Directory domain but it seems like you don't want that.

So: Have a read of the many blog posts/documentation sites that talk about Windows workgroups and the DNS behind it. Then update the Route 53 Private Hosted Zone in your VPC so that the Windows instances can discover each other.

First of all, thank you for reading this and replying for my message.

All instances are joined to Microsoft windows active directory (not aws managed directory services). Are you suggesting to use managed services?

Also DC1, DC2 and DNS servers run DNS services and I have them set up as DNS servers with DHCP option sets. However, I do not use AWS managed services. I found something that maybe a good solution - using Route53 Outbound Resolver https://aws.amazon.com/blogs/networking-and-content-delivery/integrating-your-directory-services-dns-resolution-with-amazon-route-53-resolvers/

But here is my question - Is this possible to do w/o using AWS Managed AD ? Can I simply install AD on EC2 instance and point Outbound Resolver to it?

Also, I have noticed that WINS replication is not working between the ..91.20 and ..91.21 partners. It seems that ..91.21 can communicate with ..91.20, but 91.20 cannot communicate with ..91.21 (at least for WINS purposes). Can this be also related to the problem?

Finally, if the semi traditional setup - creating DNS servers on EC2 instances and pointing DHCP option sets on them is not correct, why is it working on some instances and it doesn't work on others (I am able to ping some of the instances by the host name).

Can somebody please advise or do I need to open a separate thread for this?