Playing with VOIP

made my first (real) foray into VOIP yesterday.
I had gotten myself a Cisco
ATA 186
(eBay rocks) and decided to try and
get it working (in between studying). It wasn’t as plain and simple as I hoped it
would be, but I learnt a number of things along the way.

The first problem was that the ATA has an RJ11 telephone connector and all the phones
I had had a BT plug. I didn’t have a crimper handy, or RJ11 plugs for that matter,
so I was slightly stuck. I did try to use a modem cable (RJ11 to RJ11) plugged into
a phone, but that didn’t work as it turns out that the wiring sequence is reversed
for a modem cable. Eventually I found a BT socket I could scavenge, cut off one end
of the modem cable, and wired
up the BT socket
so I could plug a normal phone into it.

Well, that wasn’t quite the first problem. As I couldn’t get a handset working, I
wasn’t sure if the the ATA was functioning correctly. It’s a cool device and can be
configured in three ways; either with a voice menu through the handset, by uploading
a configuration file through TFTP,
or through a web interface. The only problem was that without a handset I didn’t know
whether the device had managed to obtain an IP address from the DHCP server; and if
it had I didn’t know what it way. I solved that quite quickly, but firing up my favourite
network scanner and finding out that the device had picked up an IP on my network
and was happily living there. The web interface was then accessible through SipGate which are an excellent
VOIP service which provide a geographical number so you can accept calls from PSTN/POTS
networks. You can also call normal numbers directly at reduced
and make free calls
to other VOIP networks.
SipGate use SIP for
their service, a common VOIP protocol which is supported by most VOIP phones.

Here’s where I hit problem number 2. The firmware on the ATA was for SCCP (Skinny
Client Control Protocol), not SIP (Session
Initiation Protocol), and any links I was finding on the Web were pointing me at Cisco where
I needed a username/password to download a firmware update to allow me to use SIP.
After much clever searching on Google, I managed to find a copy of the SIP
3.01 for ATA 186/188 firmware
floating around the Web. The firmware upgrade
process was quite interesting with the upgrade software running a TFTP server and
using the handset to tell the ATA to intiate an upgrade session with the upgrade software.

Once I had the ATA configured for SIP, configuring the box was simple, as SipGate have
the necessary configuration information you need:


I’m still stuck on problem 3 at the moment. I can make outgoing calls, but not recieve
incoming ones. I’ve tried redirecting the network traffic I believe the ATA needs
directly to it; however still no luck. Will give it some more time this weekend and
see if I can get it working properly

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