I have had requests several times to document the process for turning the Netcomm into a cellular "modem". In addition, the requestor usually wants instructions on how to create a private, LAN-type network using an outboard router to perform certain functions which the Ozzie Netcomm seems not to be too good at. Maybe the Netcomm works on the outback. But here in the Great White North it has apparently not been quite up to snuff.
This particular set of instructions does not really turn the Netcomm 3G25 into a cellular "modem". I'm not sure that is possible. The Netcomm has what it calls a "half-bridge" mode available. It is not clear to me exactly what that mode does. I haven't done an exhaustive search on Google for related information. As I don't own a Netcomm, I can't experiment with one either.
The basic concept here is to turn your outboard router into an ethernet switch/WiFi Access Point. We will simply replace several of the important, significant functions previously performed by the Netcomm and have the outboard router do them for us.
Note: I will not discuss here the use of third-party firmwares such as DD-WRT or Tomato, which can be used quite successfully on some types of commercially-available routers. If your router happens to use those firmwares, these directions should still apply.
The outboard router will do the WiFi functions, as this is what many users seem to want. But the outboard router will NOT do any routing, firewall functions or NAT. All of those will continue to be done by the Netcomm. I would suggest also that the outboard router do the dhcp functions, as the Netcomm seems to have a tendency to lose its DNS addresses. dhcp is what normally would configure DNS addresses on your PC. You will now get this from your outboard router, which will not loose its DNS information.
You can configure whatever DNS addresses you need into your outboard router. The subject of which DNS addresses to use is a whole other matter. Your outboard router will, we hope, maintain its DNS addresses in better form than the Netcomm. This means that it doesn't matter what the Netcomm does with its DNS addresses, our PC will get its DNS addresses as you have configured them on the outboard router!
The basic steps are:
0. to make this work, during the whole process you need to ensure you can connect your PC/MAC to the Netcomm and/or the outboard router. To ensure you can always connect, this requires that you first manually configure your PC/MAC with an appropriate IP address, subnet mask, and default gateway. At this stage, you just don't use dhcp at all to automatically configure your PC. This is because at some stages of the process, you would not be sure which device would fill your dhcp request and your PC might be left hanging without the ability to communicate.
1. this step will configure your PC so it will always be able to connect to the two devices we are concerned with during the critical stages of the configuration process. I would suggest using the following IP address parameters for your PC at this point: IP address = 192.168.1.253, subnet mask = 188.8.131.52, default gateway = 192.168.1.1. Later on, when we are done, we will return your PC to a state where it will use dhcp, as this is what is usually required in everyday use.
2. in this setup process we will always connect to the device we are configuring by ethernet cable. So, turn off WiFi on your PC/MAC, and enable the ethernet interface. Ensure you are familiar with the process of configuring TCP/IP V4 "Properties" for it, if you are on Windows. I do not use the MAC myself, so someone else will need to help us out as to what is required on the MAC.
3. you need to turn the outboard router into "just" another IP device connected to the Netcomm. So first we must ensure that the outboard router does not have the same IP address as the Netcomm router. Connect your PC to the outboard router by ethernet cable. Connect to the web management interface on the outboard router at whatever IP address the router has currently. Change the outboard router IP address to 192.168.1.254, subnet mask 255.255.255.0, default gateway 192.168.1.1. The latter address parameter (default gateway) sends all routing requests coming into the outboard router to the Netcomm. Please refer to the documentation for your outboard router at this point for further words of wisdom on your likely experiences in doing the above.
2. now connect the Netcomm RocketHub to the outboard router using an ethernet cable. You will need to connect the ethernet cable from one of the LAN ports on the Netcomm to one of the LAN ports on the outboard router. Do not connect to the WAN port on the outboard router.
3. using your PC/MAC (which should still be connected to the outboard router by ethernet cable) log into the Netcomm management web interface at 192.168.1.1. This next request may be a lot to ask (now! RTM!!!) but please refer to your Netcomm documentation at this point to determine what I am posting about here. Disable WiFi and dhcp on the Netcomm. At this point, when you commit these commands, the Netcomm will likely reset/reboot, and you will loose contact with the device for some time, probably as much as a minute. After a reasonable pause, just try to reconnect to 192.168.1.1 to confirm your changes have actually been completed.
4. now, your Ozzie Netcomm should blissfully be connecting to the cellular network for you, and should be routing between the Internet and your network, which you have just set up and configured. So now you should be able to return your PC/MAC to its previous state, toss some shrimp on the barbie, crack open a Fosters or two, and live happily ever after........
PS: I highly recommend that now you may want to take your PC/MAC and return it to getting its IP addresses using dhcp. Remember "Properties" for TCP/IP V4. Also, you will need to enable the WiFi interface on your PC/MAC, disable the ethernet interface (if you choose) and then try out the whole thing to see if my directions, (or your reading of them) really, really works.
If things don't work, it could well be the former is the problem. Please remember I am doing this entire diatribe from memory, and at the request of one Forum member who sent me a PM asking for instructions on how to do this very thing.
Hopefully I have succeeded. If not, I do invite any and all of you to please let me know.