How does VPN server bridge client to rest of network?

garryshape
garryshape used Ask the Experts™
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If I setup a Windows 2016 VPN server, how do clients connecting to it get to access the rest of the network?
Is there something you’d configured on the VPN server to tell it to forward DNS requests?
Or does it forward connections back to the main outside firewall?
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Usual practice is to have the VPN client machine obtain a DNS server from the VPN server. Typically, this is done via DHCP. Once connected, a client machine uses the DNS server on the site it is connected too, for all requests.

The client can be configured to either send ALL traffic down the VPN tunnel, or just the subnet in use, depending on what you want to do.
"Batchelor", Developer and EE Topic Advisor
Top Expert 2015
Commented:
In general there are two kind of VPN "servers":

On devices (like Cisco or Juniper) usually a transfer network is used, which is different from the LANs on both sides. Then all is based on routing. This works well if the "server" side device is the default gateway anyway.

Windows VPN server uses an IP pool either statically defined or fetched by DHCP. The former might give out IPs from a different or the same network, while latter always will provide LAN IPs.
Then it acts as an IP proxy, that is each traffic arriving from LAN for the VPN IP(s) are forwarded to the client, and incoming traffic is treated as it came from the VPN server machine itself.

As a side note: DNS, if provided with the VPN, needs to have priority over local DNS settings to be used. If it does not, only IP addresses can be used. But providing DNS with VPN also means that all DNS requests are forwarded to the VPN LAN, which might be considered as an information leak.

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