UPDATE
I've now had the Virgin Media cable internet service for over a year and it's superb. I upgraded to the 150 Mbps service a few months back and now regularly get in excess of 160 Mbps downstream and 10 Mbps upstream. The service seems quite reliable: in a year there have been two or three dropouts and most problems are solved by resetting the cable modem.The only problem is if you do need assistance on anything technical particularly anything Linux, DNS etc. related then be prepared to do battle with a numpty with a script in some distant Indian call centre.
13 November 2014
Introduction
I've been wanting high-speed broadband for some time and sadly my old ISP (the wonderful and extremely geek-friendly Zen Internet) are unable to provide it to my location in central Manchester any time soon. So I recently took the slightly reluctant decision to move over to Virgin Media's cable internet. The installation went ahead two days ago.Now I have a slightly geeky setup which involves an IP PBX which I will write about in detail some other time but which has two "lines" connected to it: an ordinary analogue (POTS) phone line and a VoIP (SIP) service resold by a company called ip chitchat. This works absolutely fine and the POTS line receives inbound calls and outbound ones go out via the VoIP service. In order to get the VoIP service working originally on my old ADSL setup I had to configure my router (a Netgear DGN-1000). This was to allow incoming SIP requests to my IP PBX (NATed behind the firewall) and subsequent RTP traffic to the SIP end-point making or receiving the call. For security I restricted the source IP addresses allowed to connect to those ports to those of the VoIP servers. If you don't do this you can get a combination of either not being able to receive inbound calls or being able to make or receive a call but not getting voice in one or both directions.
The Super Hub
As part of their bundle Virgin supply a Super Hub. This is a badged/mask programmed router, firewall and wireless base-station. It's very sleek and nice looking and I'm sure it's adequate for the needs of 99% of Virgin's customers. But I'm not part of the 99%. Sadly it doesn't support VoIP nor can it be configured to as even the advanced options available in its configuration pages aren't.The bad news is that the Super Hub acts as the cable modem: i.e. it is necessary to have it in order to connect to the cable network. So unlike ADSL you can't just bin it and get something else. However, not all is lost, but sadly this next bit will cost you money. The Super Hub comes with the option of enabling modem mode. In this mode its routing, firewall and wireless functions are disabled.
So the solution I used for my non-standard requirements was to turn the Super Hub in to a cable modem and then supply my own router, firewall and wireless base-station.
Bricking your Super Hub
Get a router
In order to get VoIP running you will need a new router. Experience of running VoIP through NetGear routers with an ADSL connection suggests that a NetGear router would do the job although I haven't tried this. I've also had a recommendation of Zyxel routers from someone else who has solved this problem on cable. I went to see my chums at MicroDirect who had a special offer on the Asus RT-N66U. This is a slightly pricey unit, but very nice.If anyone has any recommendations or caveats about what works then I will happily maintain a list.
One thing I would advise if you are looking for a router which will handle VoIP is to make sure that when reading round the subject on-line you ignore anything which is more than a couple of years old because it is very likely out of date.
In extremis if you have a spare Gigabit Ethernet card and a Linux box or spare PC which can be turned in to one you can make your own router/firewall. This actually is considerably simpler than it sounds, but of course still gives you the problem of not being a wireless base-station.
Now brick your Super Hub
If you've spent any time configuring the Super Hub already (e.g. with a different address range, DHCP pool etc.) then it it probably worth backing up the configuration before you do anything else.So, to brick your Super Hub (and please note that this is for information only, this worked fine for me, but don't blame me if it doesn't for you etc.) follow the instructions on the Virgin website.
This will turn your Super Hub in to a cable modem, turning off the routing and wireless features. So note that as soon as you do this you will lose internet access so if you are likely to need to look anything up make sure you've loaded it in advance.
Also note that when the Super Hub is bricked in to modem mode its DHCP server no longer works and its IP address changes to 192.168.100.1.
Configure your router
You will need to connect the WAN port of your router to the MODEM port on the Super Hub (the other ports are disabled). All I needed to do on the Asus router was set the WAN connection type to Automatic IP (as opposed to PPoE etc.) and it sprung in to life.Alternatively if this doesn't work you may also need to set the WAN IP address on your router manually to something in the range 192.168.100.0/24 with subnet mask 255.255.255.0 and default gateway 192.168.100.1 and primary and secondary DNS of 194.168.4.100 and 194.168.8.100.
I also configured the DHCP server to allocate exactly the same addresses to the various devices on my LAN as under the previous regime.
So we now have:
Configure your firewall
Having paid for the router I was disappointed to read various (old) postings about trouble getting Asus routers working with VoIP and I was dismayed that I couldn't find anything obvious in the Asus's web-based configuration which allowed me to permit various inbound IP addresses through the firewall. But to my amazement it just worked. First time. Without any special configuration. I could make and receive VoIP calls with bidirectional voice. Evidently the Asus firmware must have been updated since the earlier posts and now it just "understands" VoIP.Your mileage may vary, particularly depending upon the manufacturer and model of router you are using. But I'm a very happy customer.
Test your configuration
As with any activity which potentially opens up the firewall on an internet-connected router you should always check security (particularly if it works suspiciously easily out of the box as above).That would be another article some other time but a good place to start is to do a port-scan using the excellent Shields Up application from GRC.
