The setup: a remote network at the TV transmitter, with Internet access both through a commercial provider and a dedicated, but increasingly unreliable, microwave T-1 link to the studio.
The goal: mimic the behavior of the microwave T-1 (though not the unreliability, of course) using the commercial provider's service. Set up a "virtual wire" between the network at the transmitter and the transmitter at the studio.
I've chosen an IPsec VPN to do this, and I've set things up largely as in Ch. 35 of Linux Home Networking. At the present time I've managed to achieve bidirectional communication between hosts (but not the routers/firewalls) on each network, but to do that I had to set up a private test network as shown below.
With this setup, I can achieve bidrectional communication between both networks. Host A can reach Client VM, and Client VM can reach Host A.
Here is the relevant ipsec.conf on Router VM:
# # File: /etc/ipsec.conf # # VPN Test Router VM side config setup protostack=netkey oe=off nat_traversal=yes # LEFT: Studio # RIGHT: Transmitter conn nettonet left=192.168.152.188 # Public Internet IP address of the # LEFT VPN device leftsubnet=172.16.1.0/24 # Subnet protected by the LEFT VPN device leftrsasigkey=*removed* right=X.X.X.10 # Public Internet IP address of # the RIGHT VPN device rightsubnet=10.1.1.0/24 # Subnet protected by the RIGHT VPN device rightrsasigkey=*removed* rightnexthop=%defaultroute auto=start
Note here that I'm using RSA keys, rather than PSK's. The key signatures have been removed for security.
The ipsec.conf on Transmitter Firewall is slightly different:
Here you'll notice that the argument to
# # File: /etc/ipsec.conf # # Transmitter Firewall Side config setup oe=off protostack=netkey nat_traversal=yes # LEFT: Studio # RIGHT: Transmitter conn nettonet left=10.1.0.2 # Public Internet IP address of the # LEFT VPN device leftsubnet=172.16.1.0/24 # Subnet protected by the LEFT VPN device leftid=192.168.152.188 leftrsasigkey=*removed* right=X.X.X.10 # Public Internet IP address of # the RIGHT VPN device rightsubnet=10.1.1.0/24 # Subnet protected by the RIGHT VPN device rightrsasigkey=*removed* auto=start # authorizes and starts this connection # on booting
10.1.0.2, which is the public (again, these IP's have been obfuscated for security's sake) address of Studio Firewall. This is because Router VM's ultimate path to the Internet is through Studio Firewall via NAT.
Speaking of NAT, I should point out that there is no NAT of any kind being performed (currently) on Router VM or Transmitter Firewall. Instead, the entire 172.16.1.0/24 network is visible to the 10.1.1.0/24 network at the transmitter, just as any other public network would be.
I'll note that this does not accomplish the stated goal at the beginning of this post: set up a "virtual wire" between the 10.1.1.0/24 network at the studio and the 10.1.1.0/24 network at the transmitter. It may turn out to be the case that this "virtual wire" is extremely complicated with regard to routing and suchlike (since we would be using the same IP block on both ends) . What this does give us, however, is a place to work from.