@IanF2 Welcome to the Rogers Forum. Looking at the CGNV4 users manual, there is no user facility to enable/disable the SIP/ALG. So, as with our Hitron series modems at the current time and as indicated above, you will have to call your tech support to disable the SIP/ALG. The next version firmware for the Rogers CGN series and CGNM-3552 gigabit modem will have a user selectable SIP/ALG enable/disable function. So, that is something that you could suggest to the Virgin Media tech staff.
Baring that, what you could try is to use a third party router. Connect the modem - router - VOIP device to one of the ports, set up the router in full router mode and when you set that up, copy the VOIP devices's MAC address in the router. There should be a function to duplicate a connected devices MAC address in the router.
Then, in the CGNV4's user interface, navigate to BASIC .... DMZ which is the control page for the demilitarized zone. Enable the DMZ and then add the VOIP device, or in this case the router. The DMZ host is the end device that you want to add to the DMZ. That will be the VOIP device, or in this case the router as it will have the same MAC address. Save the changes and reboot the modem.
If your not familar with the DMZ, its an unprotected zone, so you will need the router's firewall to protect the VOIP device. The DMZ is not protected by the Hitron's firewall.
There is no guarantee that using the DMZ will work. With any other router I would say that it should, but with the Hitron modems, all bets are off. The first step is to try tech support. Disabling the SIP/ALG to enable the VOIP device is very common, too bad there wasn't a user selectable function built in from day one.
As a Hitron user, you should be aware of the latency to and thru the modem. Those are two separate issues. If you are running the modem in Gateway (router) mode, run an ipconfig/all command at a command prompt. Determine what the Default Gateway address is and then ping both IPV4 and IPV6 Default Gateway Addresses. Use something like 1000 pings to see the range of results. If your Default gateway address is 192.168.0.1 for example:
ping -n 1000 192.168.0.1
That should provide a good demonstration of the latency to the modem. That was corrected last year for the Rogers CGN3ACSMR modem.
The latency thru the modem can be seen in the first two to three rows of images from my image library. These were taken with a 32 channel Hitron CGNM-3552 modem. The CGNV4 is a 24 x 8 channel modem so its not very far behind in terms of latency thru the modem.
Those plots show the ICMP latency from the pc to the modem, out to the CMTS and back thru the modem to the pc. This is a problem that affects all data types as far as I'm aware and is caused by the choice of processing the data thru a CPU software based process versus the chipset hardware processor. This is probably common to all Puma 6/6MG based modems, and applies to the Hitron CGN series modems. From my reading, it looks like it also applies to the Virgin Media SuperHub 3 that all of the users are complaining about. That modem should be a direct Puma 6/6MG descendent of the Arris product line. Fwiw, users in North America and in the UK are complaining about the latency of these Puma 6/6MG modems. If you look at any of the latency plots posted by SuperHub 3 users, that is normal for a Puma 6/6MG modem. If you look at the last plot on this page by davidmsims, you can see the difference between the Superhub 3 on the left and Superhub 2ac on the right. The port flapping which shuts down the ports and restarts them is a different issue which has also been resolved by Rogers, although it had slightly different symptoms. You can see that indicated by the red packet loss indications.
At the present time Rogers and Hitron are working on firmware changes to resolve the latency thru the modem. Its a work in progress but I'm hoping to see a substantial change for all data types in the near future.
So, why should you be concerned? Running a VOIP device, you need stable latency. The Puma 6/6MG modem will be anything but stable. Depending on the latency thru the Virgin Media network, the overall combined latency might be a real problem. Its hard to say until you actually get the VOIP device up and running. But, if you can get tech support to disable the SIP/ALG with a simple phone call, and have trouble maintaining calls with the VOIP device, consider the issue of the combined network and modem latency. I'm assuming that you're on a Business plan with the CGNV4, and require VOIP for business purposes. Depending on the results that you get, you might want to consider a different modem.
Detecting the latency is fairly simple. In a nutshell, download and install pingplotter. Use that to ping the CMTS, which is the IP address that follows the modem's IP address in a trace to anywhere. Assuming that you have the modem running in Gateway (router) mode, the second IP address in the trace is the CMTS. You can use pingplotter to see that, or simply use a ping command and set it to run something like 1000 pings or more. That is the opposite to the ThinkBroadband approach, which uses a central server to ping the modem or pc. This approach simply goes out the CMTS and back to demonstrate the latency thru the modem. It takes out all of the other latency due to the ThinkBroadband and Virgin Media networks and any other problems that are due to the networks. Personal opinion, its a better approach to this particular problem. Run the ping tests using both IPV4 and IPV6 addresses for the CMTS to see the effect for both.
If you have a look at the following post, you can read thru the instructions on how to set this up: