On Sun, 17 Apr 2022 08:32:23 +0100, Terry Coles wrote:
> is the network set up by
> the VPN Server to forward remote traffic on and each device on the
> WMT Network is allocated an address in that range

If I understand you correctly, I think you are saying that each device 
on the WMT Network is allocated an address in the range. 
This does not make sense. Why would the WMT Network devices need addresses, in addition to their ones?

More likely, the range is only used for the VPN server 
and the VPN clients, and VPN clients can simply address WMT Network 
devices directly, using their addresses. As you've 
shown, the VPN server is configured to route between these subnets, so 
that should be fine and dandy. This is how I remember the VPN working 

This works in the same way that you can communicate to, say, a Google 
server in the range from a computer that has a local 
IP address in the range Clearly, Google's servers do 
not get renumbered to suit your local network. Neither are the WMT 
Network devices going to be renumbered to suit the VPN. It is not 
necessary or useful.

The VPN clients are having their IP addresses allocated by the VPN 
server. I think it uses the VPN's own protocol as opposed to DHCP to 
communicate these addresses to the clients, but I can't remember for 
sure. Either way, the VPN server is responsible.

This also means that the VPN clients will not be getting told about 
the DNS server via DHCP, so they won't automatically use 
it. This means their traffic won't get forwarded to the web server 
automatically. If you wanted them to know about that DNS server, you 
would need to configure the VPN server to tell them about it. They 
won't discover it automatically via DHCP like an on-site network 
client would.

Be aware that VPN clients will sometimes use a VPN-provided DNS server 
for EVERYTHING, which could have the effect of intercepting DNS 
queries for traffic that has nothing to do with the VPN, which might 
break networking for things that are running on the same machine as 
the VPN client, and could cause a privacy issue. If possible, it may 
be better to configure the VPN clients so that the WMT DNS server is 
only used to query domain names that are part of the WMT network.

So, when you said:
> The VPN Server doesn't know the IP Address of the
> Webserver, but it doesn't need to because all traffic should be
> forwarded to it.

The second part of the statement was untrue. The VPN server DOES need 
to know the IP address of the Webserver (assuming you want it to tell 
its clients), because the automatic forwarding to the Webserver only 
works for DHCP clients in the local network.

It is safe to assume that on-site Visitors devices, connecting via 
WiFi, are all configured to use DHCP, both to obtain an IP address and 
to learn about a DNS server. It is not safe to assume the same for VPN 
clients. Not only have the VPN clients already got an IP address from 
the VPN server, so they won't be looking for another one, but DHCP 
works using broadcast messages, which are only received by devices in 
the same subnet.

So, given that they have addresses, the VPN clients 
cannot make use of the DHCP server. They should, however, 
be able to make use of the *DNS* server, provided that 
they are told about it.

> The DNS Server does not work for clients logged into the VPN Network
> via VPN.

Do you mean that it does not work automatically, or do you mean that 
clients logged in via the VPN cannot query this server at all. What 
happens if you say explicitly which server to query, by doing:

    $ dig @ [webserver domain name]


    $ nslookup [webserver domain name]

on a device that is connected via the VPN?

> The Webserver is inaccessible to clients logged into the VPN Network
> via VPN unless an intermediate device is used as a 'stepping
> stone'. (eg, log into another Pi and then log in to the Webserver
> from there.

Based on all of the above, I would expect that VPN clients cannot 
access the Webserver using its domain name, but they can do using its 
IP address. Is this true, or is it inaccessible even by IP address?

If the Webserver is inaccessible even by IP address, what happens if 
you try to ping it?

When a VPN client connects to the Web Server, in theory the web server 
would see that connection coming in from a address, not a one. So, it is a given that the Webserver has to be 
configured to accept connections from clients.

With that all said, that is far from the only way to configure IP 
addressing on an IPSec VPN. I'm relying on the fact I've used the WMT 
VPN in the past to fill in some of the blanks, and it is possible 
things could have moved on from that. (Or I could have misremembered.) 
Anyone coming across this thread from a web search should bear in mind 
that their VPN might be configured completely differently.


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