Pat’s Point of View

Lately I’ve been having fun (that’s a lie, it wasn’t fun at all) trying to get VOIP to work as our home phone. If you just read that sentence and are asking yourself “what’s a VOIP?”, then the rest of this post probably won’t be very useful to you. But so that you don’t leave here totally and utterly bewildered, VOIP stands for “voice over IP” and is a method of replacing a normal telephone line with calls made over the internet.

The background

When my family and I moved house recently, we decided to ditch the landline we hardly ever used and go with iiNet’s “Naked DSL”. As a broadband service it’s been pretty good, although it took ages to get connected. They throw in VOIP as part of the package, but I thought nothing of it at the time. But as often happens my wife changed her mind I realised that it was stupid of me to not have a landline installed.

Neither my ADSL modem nor router give me VOIP capability (which is not to say they don’t “support” it) so I worked out I needed an ATA (Analogue Telephone Adapter) which would turn any old telephone into teh interwebz fone. So I did a bit of hunting around and quickly found a Linksys PAP2-NA ATA on eBay, in fact there are heaps of them on eBay for a pittance. Heaps cheaper than the Belkin ATA that iiNet try to sell you.

The problem

I bought a PAP2-NA from eBay, well, Hong Kong to be precise. Installed it, which is easy if you use these instructions specific to setting up a PAP2 on iiNet. Tried it. Didn’t work. All outbound calls cut off after 30 seconds (including the ringing time).

Then I did what I should have done first, which was to do a bit more research on the Linksys device. The PAP2 in its various forms is extremely popular by all accounts, but also very dodgy in many cases. You’ll find many horror stories on the web about PAP2s from Hong Kong that don’t work, or devices that are “locked” to a specific service provider (eg Vonage) or people “bricking” their devices whilst trying to get them to work. Actually, you’ve probably read some of these stories if you’ve found your way to this post via Google.

It wasn’t looking good. What followed was a lot of mucking around and a lot of Google searches, trying to work out what might be wrong with my PAP2.

Port forwarding

One of the first things that often gets mentioned on the various discussion threads relating to PAP2 problems is the router’s firewall and NAT capability. My router is an Apple Time Capsule, which is used to share my Naked DSL connection with all the devices in our house. It’s essentially an Airport Extreme Base Station. There is no firewall, so that was not applicable, but I thought I’d better make sure the necessary ports were making it through the NAT (network address translation).

I setup the following rules in the Time Capsule, which forward traffic on the specified ports to the PAP2 (which has a fixed IP assignment in the router’s DHCP):

1. “VOIP SIP”: TCP and UDP ports 5060-5061
2. “VOIP RTP”: TCP and UDP ports 16384-16482

(To be honest, since I got VOIP working properly I haven’t gone back and removed these port forwarding rules to see if they are really necessary, so it could very well be that you don’t need to do this bit)

PAP2 logging

After a while I came across this post about logging what the PAP2 was doing so that I could diagnose the problem, and then hopefully solve it. The PAP2 doesn’t keep logs but it can spit out logs to a syslog server, which is what most network and telephony devices do.

I wasted a bit of time trying to get my iMac to accept syslog messages from an external device. Never had any luck, something was stopping it from getting the messages; potentially it had something to do with the fact that in later builds of Snow Leopard the syslogd config is different to earlier builds as well as Leopard and older versions of Mac OS X, and so there was no information out there on how to do what I needed.

So I gave up and used a Windows laptop I had lying around, installing Kiwi syslog server. In a matter of minutes I had a stream of log messages from my PAP2 so I could monitor what it was doing. (If you do this you might want to change the PAP2′s debug level so that it spits out as much detail as possible)

Firmware update

Along the way I also discovered a lot of talk about PAP2 firmware. There seem to be many different versions of the PAP2, so you need to be very careful about getting the right firmware. My PAP2 was originally distributed by Vonage and is a “PAP2-NA” hardware version 0.03.4 and had firmware version 3.1.12(LS) when I bought it. The latest version of firmware for this model is 3.1.23(LS) which you can get from here. To install it follow the instructions at the end of this post (note the firmware he refers to is for the PAP2T-NA which is a different model and that firmware will not install on a PAP2-NA).

But alas, this was merely a clever distraction from the fact that VOIP wasn’t working and I didn’t know why. The logs from the PAP2 gave no indication that there were any errors etc.

The ADSL modem

Then I started thinking about how many people kept talking about “routers” causing their problems. In my case my router (the Time Capsule) is separate from my ADSL modem. My modem is a Siemens SpeedStream 4200 left over from a previous Optus broadband package. It does ADSL2+, is easy to setup and has worked flawlessly for years. Despite these facts I was now looking at it with scorn and suspicion.

Research quickly revealed the most excellent website TheVoipStore and their information on the SpeedStream 4200. Earlier I made the distinction between a router/modem having VOIP “capability” and “support”, and it appears the 4200 does neither. Something about asymmetrical NAT, but anyway I had found the source of my “outbound VOIP calls drop-out after 30 seconds” problem. There is an easy solution, however! Put the modem into bridge mode.

At about this time I remembered that I had been using the modem’s built-in “router” to dish out DHCP to my Time Capsule which was in turn acting as a router and dishing out DHCP to everything else. No particular reason, was just the easiest way of setting it up. But I used to run another modem bridged to the Time Capsule, so I simply returned to that arrangement (following TheVoipStore’s instructions for putting the 4200 into bridge mode).

Voilà, VOIP started working instantly. Outbound (and inbound, but they were never affected) calls can be made for any length of time.

So in the end, there was nothing at all wrong with my Linksys PAP2-NA, it was the modem/router configuration all along!

I hope this tale is of some use to anyone who has part or all of the arrangement of devices described above. Best of luck.

This entry was posted on Sunday, May 30th, 2010 at 10:38 am and is filed under Ramblings. If you enjoyed this post, you might also like to leave a comment or follow @patrickkennedy on Twitter.

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