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At my company we have a Mac Mini set up in the office that we use to test out web tools. Everyone in the company has access to our VPN (L2TP over IPSec) and they access the Mac Mini while being connected to the VPN. We serve tools on the Mac Mini with various web clients.

HOWEVER, with at least a couple people, they connect to the VPN and they cannot access the web clients on the Mac Mini. I have confirmed that their settings are correct, they have "send all traffic over VPN" checked, and they can access the internet as well as other clients we have made IP-restricted (but are not on the office network like the Mac Mini). They tried pinging the IP and got a timeout.

One of the people who can't access the Mac Mini tried it out with their mobile hotspot and it DID work and they were able to access the client.

Does anyone have any idea of what to try out here? I hope that because they use AT&T as their IP that it's not just hopeless. I'm mostly looking for ways to diagnose this problem.

If it's helpful, when accessing the test Mac Mini clients, we simply use http://192.168.x.x/<toolname>.

Also, at least one of these users has an AT&T router setup, and this has caused issues with our L2TP over IPSec VPN in the past.

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This problem may be caused by both local networks using the same network mask.

For example, if the office network uses 192.168.178.0/24, and the home network uses the same (or one that overlaps with it), then the VPN client cannot setup a dedicated routing, because the IP addresses are not unique. That's why it works when using the hotspot, because then the client will be in a different local network.

To fix this, change the network mask in the office to use another network mask. Select one that is not frequently used by home routers.

Private IP address ranges:

  • Class A: 10.0. 0.0 to 10.255. 255.255.
  • Class B: 172.16. 0.0 to 172.31. 255.255.
  • Class C: 192.168. 0.0 to 192.168. 255.255.
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  • Thank you for the response! I was investigating what it would take to change the network mask, and found that we will have to update several things (services, machines, people accessing those machines and services), and found that it's quite a lot. Do you think that getting those two users to update their home router configurations to use different private IP ranges, would work to solve this issue? Jan 19, 2022 at 18:02
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    @transposeglobal of course, yes, that’s the alternative. In the end, you’ll have to remove the collisions, and either way should work.
    – not2savvy
    Jan 19, 2022 at 18:16
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    I’d recommend to set up a DNS server for your local devices, so you can address them using domain names instead of ip addresses. This helps to avoid further problems.
    – not2savvy
    Jan 19, 2022 at 18:18

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