Dual NICs and Caching Server

Question

Hi All -
We currently have a Mac Mini and utilize its caching server functionality on our "normal" subnet.  We also have a "guest" subnet which is abstracted from our normal subnet (used for guest wireless devices/BYOT).  Would it be possible to use the Thunderbolt to Gigabit ethernet adapter on our Mac Mini and have the caching server serve updates on both interfaces/subnets so we do not have to buy a separate Mini to serve the guest subnet?

Answer 1

Both networks and the server will have to have the same single WAN IP address. The following diagram shows a possible configuration that would work.
Subnet A -------------+
    |                            |
Server                     +---------- Firewall/NAT ------ Internet
   |                            |
Subnet B -------------+
The following should also work
Subnet A ---------- Server ---------- Subnet B --------- Firewall/NAT --- Internet
The above however requires the Server to act as a router to forward traffic
The following would not work
Subnet A -------------+
                                |
                               +---------- Firewall/NAT ------ Internet
                                 |                                             |
                                |                                             |
Subnet B -------------+---------------------------------- Server
With the above the Server has its own public IP address and is also directly connected to one of the internal networks. As the server has its own public IP address this will be different to the shared (NATed) public IP address that everything else is using. As the public IP addresses are different the clients will not be able to use the Caching server.