VPN not working from BT internet

[startork]

Our office VPN is not working when a member of staff is using BT broadband. The VPN works fine when using sky, virgin and mobile data but fails when using BT.

Tunnelblick returns the following Warnings:
Warning: DNS server Address 8.8.8.8 is a known public DNS server but is not being routed through the VPN

I have tried disabling the firewall and ensuring Port clamping is on.

Has anyone had a similar issue before?

Many thanks,

[Keith_Beddoe]

@startork 

Welcome to this user forum for BT Retail phone and broadband customers.

Are you a BT Business customer?

[startork]

Hi @Keith_Beddoe 

No, we are not. This is relevant for staff wfh with standard personal BT Broadband.

[licquorice]

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@startork wrote:

Our office VPN is not working when a member of staff is using BT broadband. The VPN works fine when using sky, virgin and mobile data but fails when using BT.

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Do you mean when that member of staff uses Sky Virgin or Mobile or other members of staff using those networks have no problem?

Is it just one member of staff that has a problem using BT or more than one?

You can see where I'm heading here.

[startork]

So far two members of staff with BT have tried to use the VPN and failed. Other members of staff who do not have BT have no problem.

Personally I have tested with sky, virgin, BT and mobile data and the issue only occurs on BT.

[licquorice]

If its a VPN into your office network, it seems strange to get an error message regarding Google DNS

[startork]

It seems this is the default DNS pushed by draytek, it does seem odd though.

[licquorice]

I assume the member of staff has the Draytek router.

DNS shouldn't be involved if the member of staff is creating a direct connection to your office network via a VPN.

Does the VPN sit on the Draytek or their laptop/PC?

[startork]

It is an OpenVPN connection which allows the draytek (office) router to push it's own DNS. It seems to be pushing this DNS and the device is connecting but traffic is then not being routed correctly via the VPN.

The member of staff has a BT Hub router I believe.

[licquorice]

Does the member of staff have FTTP or FTTC service?

If the former, they could try a direct PPPoE connection to the ONT to eliminate the home hub as the problem.