DNS issues with RRAS clients with two static address ranges

Question

Hello,

We have a 2012 R2 RRAS server providing VPN access to remote clients.
It uses a static pool of addresses from 10.0.0.50 to 10.0.0.80

We needed to free up two addresses from the middle of the pool of 10.0.0.65 and .66
We therefore reduced the static pool range to 10.0.0.50 to 10.0.0.64
We then added another pool of 10.0.0.67 to 10.0.0.80, so it looked like this:

We then started getting emails from several VPN users saying they couldn't access internal resources, which after some diagnosing via ping tests etc seemed to be a DNS issue (DNS servers are 10.0.1.10 and 10.0.1.11)
Our network is a /23 so it's 10.0.0.0 netmask of 255.255.254.0

Can anyone explain why DNS issues would arise by simply changing the IP pool size and adding another pool? Especially as some of those people with a problem were using an IP low in the pool such as 10.0.0.51 which is essentially in the same pool it was before.

Thanks
James

Answer 1

I think the issue may be a sudden unexpected IP conflict with another device on the network. It's possible the few users reporting the issue were assigned the conflicting IP causing a problem.

Is my method of adding ranges to RRAS correct? If so, I will split the range again, and exclude the conflicting IP to prevent future errors.

Thanks
James

Answer 2

Hello @James Edmonds

Since DNS is in a different subnet, I would definitely look in the DHCP Relay Agent settings:

https://learn.microsoft.com/en-us/previous-versions/windows/it-pro/windows-server-2003/cc758483(v=ws.10)

Troubleshooting guidance:
https://learn.microsoft.com/en-us/windows-server/troubleshoot/troubleshoot-problems-on-dhcp-client

Further:
https://learn.microsoft.com/en-us/previous-versions/windows/it-pro/windows-server-2003/cc779610(v=ws.10)
https://learn.microsoft.com/en-us/previous-versions/windows/it-pro/windows-server-2003/cc781736(v=ws.10)

Hope this helps with your query,