No WebAdmin access over VPN using public hostname

1) what happen if you ping a local computer by name, from VPN? Example ping ecxhange.LOCAL.NET

2) Is your VPN Pool (L2TP) allowed to use your UTM DNS

3) Is your VPN Pool (L2TP) under Masquerading like this VPN Pool (L2TP) -- >External (WAN)?

If the configuration is correct in webadmin settings to allow VPN Pool (L2TP), If Masquerading is Correct, and if DNS is correct you should reach the external name by internal ip

I did the test with successful result
And yes VPN users reach the internet from UTM once connected

Local DNS works fine and I can ping machines by using the internal DNS. As stated, I CAN access the WebAdmin using the internal name. This, while a workaround, is a bit annoying as it throws certificate errors.

I didn't have a DNS masquerading rule for the VPN pool... That said, adding it didn't change anything. :(

You are able to connect by public name, but that gives you a certificate error? 

What? No.

From INSIDE the LAN, I can connect using the public DNS name without any issues.

From OUTSIDE the LAN (using VPN) I CANNOT connect using the public DNS. I CAN connect using the internal DNS name, but then I get certificate errors, because the internal DNS uses internal domain names, not the public ones (COMPANY.COM vs LOCAL.NET).

With internal DNS what you mean, UTM Dns or internal server dns? Try to use UTM dns  instead.

And in UTM system settings, what you provided for hostname? Try to put there the public name

Anyway I never use windows or linux servers for DNS. If it needed for Active directory or internal purposes, in UTM "DNS Service" there is "Request Routing"

Try this way

The internal DNS being our internal DNS server. The UTM already has the public name as the host name.

I can try the request routing. I did follow the guidelines on the DNS config section, where it says that if there are internal DNS servers then the UTM DNS should be left blank.

this are the simple steps to configure it correct
And dont forget, flush your dns cache

this are the simple steps to configure it correct
And dont forget, flush your dns cache

This sounds like a good idea, in general, and I'll see about implementing it. I do, however, need to be on-site for this, so this'll have to wait till Monday... Till then I'm left accessing the WebAdmin via the internal DNS name as before.

One extra question... while I definitely plan to use the UTM as the DNS server, I fail to see how that will resolve the issue with the WebAdmin access over VPN.

So, OK, the UTM will be the DNS, but it'll still resolve the public DNS name as the public IP and internal name as the internal IP... which means that I'll be getting the same errors I am getting right now (access over public DNS name is blocked while access over local DNS name is permitted, but doesn't match certificate).

About the only thing I can think of is to add a static DNS entry for the WebAdmin to always use the internal IP (overriding the public DNS name), so if the UTM DNS is used after someone connects via SSL, then it'll work. That's assuming the VPN client does, in fact, use the VPN DNS and not the primary DNS of the machine...

So, to summarize, how will that help solve the WebAdmin access problem?

You are right about certificate error, but i think static dns for External IP should work

OK, I've spent some time today reworking our DNS servers (there was actually a good reason to do so, as one of our DNS servers, which was supposed to be publicly facing and serving only public DNS records was misconfigured and wasn't publicly facing nor was it serving the right records). As such the UTM is now our primary DNS server with redirects to our internal AD DNS servers, as you suggested.

I've since removed the public DNS name for the WebAdmin and instead created a new, static entry, in the UTM itself. Suffice to say, things are working exactly as I'd like them to. :)

Thanks for the help!