Home » Technology » Internet/Web » Deploying Voice Over Wi-Fi with Asterisk

The Most Versatile VoIP Provider: FREE PORTING

Deploying Voice Over Wi-Fi with Asterisk


Getting Wi-Fi to play nice is another one of those grammatically incorrect, but thorny Linux problems that Asterisk® inherits because of its roots. In the Windows and Mac worlds, we've become accustomed to plug-and-play for things like Wi-Fi USB sticks, but it ain't that easy with Linux unfortunately. Once you get the right device, this project will take you less than 30 minutes to complete. But we've invested almost a week getting everything to work ... so you won't have to. If the Linux community ever wants to see Linux used as a desktop PC, this piece of the puzzle needs some work! Even with the correct hardware and drivers, there is virtually nothing available on either the net or in the 1,000 page Linux tomes that makes this project simple. Admittedly, we're anything but Linux gurus, but we can read. And it shouldn't be this hard to find the answer to the following simple question: how do I set up a WiFi connection on my Linux box. Now that we know how, we would hasten to add that you shouldn't have to bury code in numerous obscure places in the operating system and issue dozens of unintelligible Linux commands to make a Wi-Fi adapter come to life! So, why do it, you might be asking. Keep reading, and we'll get to that.

Who needs it? Anyone in the emergency preparedness and continuity of operations business oughta have a WiFi PBX in their suitcase! Can you spell K-A-T-R-I-N-A. And if you or your organization wants the flexibility of an instant, high performance telephone system on a moment's notice, then WiFi is a must-have. Ever been to a convention with your entire office but didn't want to leave all your phones behind? Now you don't have to. Using Wi-Fi IP phones, this entire phone system can be deployed WITH NO WIRES using a battery-operated notebook computer or, better yet, a small-footprint PC (see inset) plugged in to a $200 generator or a low-cost UPS if electricity is flowing. And someday we may get Asterisk running on our Nokia 770, but not this year.

What to Use. The easiest solution for Voice Over Wi-Fi is a WiFi USB stick and an Asterisk@Home server. Why USB? Because you can use it with almost any modern PC on the planet without having to install a card in the machine. There are now close to two dozen different WiFi sticks available at stores such as CompUSA, MicroCenter, and Fry's. The only problem is the scarcity of Linux drivers for ALL of them. Luckily, there is one chipset that works without a dog-slow Windows driver emulator (such as ndiswrapper): the ZD1211 chipset. Both the Safecom SWLU-5400 and SWLUZ-5400 have this chipset. The real beauty of this USB adapter is that it can function as a host in an Ad Hoc Wi-Fi network, or it can be configured in Infrastructure Mode to take advantage of an existing Wi-Fi access point serving as a Master. The device also can be configured as a Master or Repeater and supports both WEP and WPA encryption as well as 802.11B and G. Bottom line: This WiFi stick has the flexibility to function in virtually any type of existing or newly created Linux Wi-Fi network. That was our theory anyway. Read on.

Where to find one. Finding the right product turned out to be the easy part. If you're in the U.S, the more difficult task is finding a USB adapter with this chipset. In Europe, they're a dime a dozen. While they are FCC approved and include a chipset manufactured by Texas Instruments, they're almost impossible to find stateside. One possible source is eBay. Search for Safecom USB WiFi and be sure to check the Search title and description box. There's almost always at least one for sale. If not, check back in a day or two or request an email when one is listed. With shipping, you should be able to find one from various U.K. distributors for about $30. Be sure the ad states that the product uses the ZD1211 chipset, or you're wasting your money. NEWS FLASH: IOgear now makes the GWU523 which reportedly has the same chipset (although we have not actually tested one). Here's the PriceGrabber link of sources. One that we now have tested with the same chipset is AirLink's AWLL3026 which is on sale this week at Fry's or Outpost.com. If you get in a crunch and can't find one, contact us. We have a few spares (not on sale) that were used only to verify that they worked.

Wi-Fi Deployment Issues. There are many ways to deploy a Wi-Fi network and adding an Asterisk PBX to the mix just multiplies the number of available choices. To keep things simple, we've chosen what we believe is the easiest approach, but your needs may vary so we'll point out other options as we go along. We're assuming you have an Asterisk@Home 2.2 server already running because it's the easiest way to deploy Asterisk on the Linux platform. CentOS/4 is built right in. Here's our 90-minute step-by-step guide if you need it. We're also assuming you have a WiFi access point or router (802.11B or 802.11G) already in place and working with at least one wireless device. If not, start there and come back.

Our Wi-Fi lab (aka home) and test server for this project may or may not be typical. The PC is an EZgo which is roughly the size of a Mac mini or about 4 stacked CD cases (see inset above). You can see the USB stick hanging out the back of it. It's only about 2 inches long. And, yes, I hear someone asking, "Why not just use a Mac mini?" The short answer is that, while Asterisk runs on the Mac, it's no walk in the park. And, by the time you build a Mac system with the tools bundled in Asterisk@Home and get them all talking to each other, even my kids may be out of college. Let's just say you will quickly come to appreciate the real beauty of Asterisk@Home. For another painful approach to building a small-footprint Asterisk system, check out Tom's Networking. No, thanks.

We have a fairly large house so we have a WiFi router at one end and a Wi-Fi access point at the other. The two devices are hard-wired together with a 100 megabit, CAT5 network cable so they're both on the same network segment: through Several dozen devices are scattered around the various rooms on the three levels of the house to keep me entertained but mostly to keep me out of the Little Mrs. hair. A burglar's paradise, you might be saying ... well, yes, except we'd get your picture on the way in and out.

The ESSID on both WiFi Masters is the same: MundyLANd. You need this setup for moving around a large WiFi network. The trick is that one unit operates on WiFi channel 1 while the other is set to channel 11. That way the signals don't step on one another, and your client device has the smarts to transparently switch from one access point to the other when it needs to... much like cellphones moving between cellphone towers. For purposes of this article, we will assume that your devices operate with 128-bit WEP encryption since it's the easiest to configure. Note: We didn't say WEP was secure. We just said it was easy to configure.

In the middle of the house, we have a new addition from Santa, a Sony wireless TV that operates as a Master on WiFi channel 6. We'll have more to say about it in a future column. And, yes, we still hate Sony after their rootkit fiasco! But Santa didn't know any better, and who are we to turn down free toys. Why is it that Sony never acted this way until an American took over the top job at the company? I'm sure our European and Asian readers will have a quick answer.

For now, what you need to know is that our home maxes out ALL of the existing U.S. WiFi channels, much to the chagrin of our closest neighbors. Because of the overlap between Wi-Fi channels, the only practical channels to deploy are 1, 6, and 11. This becomes important for this project because we want to make sure the new Linux Wi-Fi dongle plays nicely by not using an intermediate channel or, worse yet, the Sony WiFi channel (6) which doesn't provide access to the Internet without knowing a different ESSID and password, both of which are about as long as your arm.

The reason for this lengthy diatribe was to lay the groundwork to get you thinking Wi-Fi, and it also exposed the only technical wrinkle we observed in this project. When configured in Managed mode, the Safecom USB WiFi adapter is supposed to seek out the nearest access point and set itself to that channel. It doesn't. Our experience using this Linux driver with CentOS/4 which is bundled with Asterisk@Home 2.2 has been that this rarely works as it should. The channel selection appears to be almost totally random. When the device sets itself up on the wrong channel, all sorts of ugly things can happen. For openers, you probably won't get the network connectivity you expect. Many of the Macs and PCs in our house couldn't talk to the WiFi-enabled Asterisk box until we got the adapter correctly set to the channel of the nearest WiFi Master, channel 1 in our case. Obviously, if the device configured itself for Channel 6 or a nearby channel, we were out of luck ever talking to the box. That turned out to be a headache, but we'll show you a little discovery we made that makes it less painful. Just be aware that this may be a manual drill each time you reboot the WiFi Asterisk server or move it (not often, if you're smart!). We've had much worse luck with Windows PCs and WiFi devices over the years, so this really wasn't a deal breaker in our book. Connectivity works. The Linux driver works. Encryption works. And the phones ring. Those were the critical pieces in this puzzle from our perspective. Now on with the countdown!

Downloading the Linux WiFi Driver. After obtaining the hardware device, the next step is finding a Linux driver for it. There happen to be two, and someday when our hair grows back, we may try the other one. In the meantime, you'll need the Linux zd1211 driver which is available from SoureForge. Just find the site closest to you and download the compressed tarball from here. Here's where you'll find the other one just in case someone else enjoys water torture. Wasn't that easy? Well, not so fast.

Once you unzip and untar the driver bundle (tar -zxvf zd1211-XXXX.tar.gz), you'll find a README file which is actually pretty good. It only leaves out one little thing: the device name of the WiFi dongle on your Linux box. The answer is wlan0 (that's a zero on the end) so write it down. You're going to need it ... a lot!

Compiling and Installing the WiFi Driver. Now we're getting to the fun part. We're assuming you will be installing this on a freshly installed Asterisk@Home 2.2 system built using the ISO image. You can read all about how to do that here. Will it work with another version of Asterisk@Home? Maybe. Try it. Heh heh! This isn't the Windows or Mac world so drivers have to be compiled for the Linux box on which you wish to run the software using the Linux kernel that was in place when you compiled the software. So, here's gotcha #1. If you ever get an updated kernel with CentOS/4 (as you will when you run yum -y update after installing Asterisk@Home 2.2), you will need to repeat this drill and recompile and reinstall the driver. HINT: Run yum -y update on your Asterisk@Home 2.2 server before continuing! Now you see why Linux folks aren't overly enthusiastic about kernel upgrades.

To begin the WiFi driver install, just rename the downloaded driver folder from SourceForge to zd1211 and copy it to a safe place on your Linux machine while logged in as root, e.g. /root works great. Now switch to that folder (cd /root/zd1211) and issue the following commands to compile and install the driver:

make install

Once this finishes, you'll need to manually load the driver. The README has some pretty good hints about this, but no cigar. Finding the correct answer requires that you first know the question to ask: find / -name *zd1211*.ko. This tells us where to find the little cream puff we want to load. Keep in mind that the "answer" will be different each time the Linux kernel version changes. If you're not running 2.6.9-22.0.1.EL, then this won't work. So how do you know which kernel you're running? Just type this simple (but obscure) command: uname -a. Now let's load the USB driver:

insmod /lib/modules/2.6.9-22.0.1.EL/net/zd1211_mod.ko

Once you've loaded the driver, we need to be sure it really, really is loaded: lsmod | more. Just scroll down the list with the enter key until you see an entry that starts with zd1211. Then press q to quit lsmod.

zd1211_mod 191876 0

Are we there yet? Why no, we're just getting started. Isn't Linux fun!

Firing Up the Wi-Fi Adapter. Actually, we're closer to being finished than you may have thought. There are just a couple more steps. We want to manually make sure things are working. Then we'll need to configure Linux to automatically load the WiFi driver each time you reboot your system. You'll find it's easier to get the kinks out of network drivers by first doing things manually, and then recording what you've done for posterity. For openers, you'll need an IP address for this WiFi adapter. That address obviously needs to be on the same subnet as the access point with which it will be communicating. For purposes of this example, we've chosen on the subnet of our WiFi router which has IP address YMMV. You also need to know some other things such as the subnet mask, the router's IP address, and an IP address for your DNS (name) server, but we'll get to that. Once you've chosen an IP address, let's fire up the adapter and then check to be sure it's running:

ifconfig wlan0
ifconfig | more

You should get a response that looks something like this:

lo Link encap:Local Loopback
inet addr: Mask:
inet6 addr: ::1/128 Scope:Host
RX packets:12146 errors:0 dropped:0 overruns:0 frame:0
TX packets:12146 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:985362 (962.2 KiB) TX bytes:985362 (962.2 KiB)

wlan0 Link encap:Ethernet HWaddr 00:E0:98:F2:BB:40
inet addr: Bcast: Mask:
inet6 addr: fe80::2e0:98ff:fef2:bb40/64 Scope:Link
RX packets:10638 errors:0 dropped:0 overruns:0 frame:0
TX packets:3483 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:1301983 (1.2 MiB) TX bytes:335569 (327.7 KiB)

You'll see that wlan0 is in the list, and it has the IP address that we assigned. That's good news. You'll also note that there is no eth0 device shown even though our machine has an Ethernet adapter built into it. This is another little gotcha to keep in mind. Make sure, if your box has an internal Ethernet adapter, that you configure the main adapter to use DHCP to obtain its address. You do this by issuing the command netconfig and using the space bar to choose Use Dynamic IP Configuration. Then tab to OK and press Enter. The reason for this is very important. Lots of Linux software makes the assumption that eth0 is the default network adapter if it happens to be running. So we want to make sure it isn't running by unplugging the Ethernet cable before booting the machine. If you have a fixed IP address for eth0, then it will load eth0 whether a cable is connected or not. If you configure eth0 for DHCP, then eth0 will not be loaded unless an IP address can be obtained from a DHCP server. With the cable unplugged, you're pretty safe. So, if your machine is showing an eth0 device, reconfigure eth0 for DHCP, and reboot the machine. Then reissue the ifconfig command after logging back in as root. When your display shows two network devices like ours (loopback and wlan0), you're ready to proceed. Another clue: When Asterisk@Home starts up and you log in to your server, it normally tells you the IP address for accessing the Asterisk Management Portal using a web browser. This gets broken when you're using a Wi-Fi adapter that isn't on eth0 because Andrew's setup is merely regurgitating the IP address of eth0. Don't worry! It still works when you enter the correct IP address of your WiFi adapter.

Configuring the WiFi Adapter for Your Wi-Fi Network. Now that we have the WiFi adapter running, we'd like it to communicate with the WiFi network in our home or office. You obviously have to have a WiFi network up and running in your home or office for this to work. But we'll assume you've taken care of that little detail. 25+ years in the technology business has taught me to restate the obvious once in a while just in case something isn't quite as obvious to others. What we'll need now is the name of your WiFi network, the ESSID. And we need to know the channel on which your nearest WiFi access point is broadcasting. Finally, we need a way to identify this access point if you have more than one. Lucky for us, there's a Linux command that will tell us everything except your WiFi WEP password if you're using WEP encryption on your wireless LAN (you are using some sort of encryption, aren't you?).

iwlist wlan0 scanning

You'll get a result that looks something like the following:

wlan0 Scan completed :
Cell 01 - Address: 00:06:25:55:C4:E3
Frequency:2.412GHz (Channel 1)
Quality:68/92 Signal level=54/154 Noise level=0/154
Encryption key:on
Bit Rate:1Mb/s
Bit Rate:2Mb/s
Bit Rate:5.5Mb/s
Bit Rate:11Mb/s

Cell 02 - Address: 00:01:4A:10:EE:60
Frequency:2.437GHz (Channel 6)
Quality:4/92 Signal level=35/154 Noise level=0/154
Encryption key:on
Bit Rate:1Mb/s
Bit Rate:2Mb/s
Bit Rate:5.5Mb/s
Bit Rate:11Mb/s
Bit Rate:6Mb/s
Bit Rate:9Mb/s
Bit Rate:12Mb/s
Bit Rate:18Mb/s
Bit Rate:24Mb/s
Bit Rate:36Mb/s
Bit Rate:48Mb/s
Bit Rate:54Mb/s

Cell 03 - Address: 00:09:5B:2A:A2:AC
Frequency:2.462GHz (Channel 11)
Quality:4/92 Signal level=36/154 Noise level=0/154
Encryption key:on
Bit Rate:1Mb/s
Bit Rate:2Mb/s
Bit Rate:5.5Mb/s
Bit Rate:11Mb/s

Here's where things get a little buggy. You're supposed to be able to set the the ESSID, the broadcast Mode, the access point and the WiFi channel for the zd1211 using the Linux iwconfig tool. As mentioned previously, in standard Managed mode (meaning you'll be connecting to an Access Point on your WiFi network), you have no control over the channel or the access point. The theory was that the adapter would set itself automatically. Unfortunately it doesn't although your mileage may vary if you have only a single access point within range of your zd1211.

As we indicated on the front end, our WiFi network is somewhat atypical. So the best solution for you is to execute the following commands and see what happens on your own wireless LAN:

ifconfig wlan0 (use your designated IP address)
iwconfig mode Auto
iwconfig wlan0 essid "MundyLANd" (use your ESSID)
iwconfig wlan0 key F57EC678F1B061BAC59EC593EFE (use your WEP key)
iwconfig mode Managed
iwlist wlan0 scanning (reports the cell numbers of each access point in range)
iwpriv wlan0 connect 01 (use the cell number of the access point closest to your zd1211)
iwlist freq

Now go to another machine in your network and see if you can ping your WiFi Asterisk@Home box:

ping (use the IP address of your WiFi AAH machine)

If you're successful, great! Reboot your WiFi AAH machine and repeat the test. If it works twice, you're probably safe skipping the next section.

Forcing the WiFi Adapter to a Specific Access Point and Channel. If you're getting random results with the above approach, then here's the solution that works. Unfortunately, it requires a set of eyeballs each time you reboot your system unless there's only one access point within range of your Asterisk Wi-Fi box:

ifconfig wlan0 (use your designated IP address)
iwconfig mode Managed
iwconfig wlan0 essid "MundyLANd" (use your ESSID)
iwconfig wlan0 key F57EC678F1B061BAC59EC593EFE (use your WEP key)
iwlist wlan0 scanning (reports the cell numbers of each access point in range)
iwpriv wlan0 connect 01 (use the cell number of the access point closest to your zd1211)
iwconfig (should show the MAC address of the access point from step above)
iwlist freq (should show the channel in use that matches your access point's broadcast channel)

To be sure you have connectivity on your local area network, issue this command: ping using the correct internal IP address of your own router/firewall.

This setup should work every time except you have to manually look at the results of the scanning report to decipher the proper cell number because the order of the list can change each time you run it. If only one access point is reported, you're in luck! Just test it several times to be sure. Once you're sure, you should be safe in executing the iwlist wlan0 scanning command followed by iwpriv wlan0 connect 01. Don't skip the scanning step, however, as this appears to "prime the pump." One other word of warning: don't execute the scanning command without first assigning an IP address to wlan0 using ifconfig, or you'll get an unrecoverable kernel panic.

That about covers all the gotcha's. The important lesson here is to get the network connectivity stable before you automate the process so that it autoloads when you boot your system. If you can't get stability in the channel and access point connectivity, at least make certain that you understand the limitations of your solution before making things automatic.

Adding Internet Connectivity. We haven't mentioned getting out to the Internet yet. For that to work, you'll need access to a name server (aka DNS). Here's another little Linux "feature" to bite you. The interactive mode of netconfig is designed to handle the eth0 interface. To get things working on the wlan0 interface, issue a command like this:

netconfig --gateway= --ip= --nameserver= --netmask= --device=wlan0

Be sure you adjust gateway (IP address of your router); ip (IP address of your new Asterisk box); nameserver (from a Mac or Windows machine: here's how to find it; on a Linux machine: nslookup mundy.org returns your DNS server's IP address on first line following Server:; netmask (you can find this with iwconfig); device=wlan0 (leave this alone). By the way, you only have to execute this command once, not every time you boot your system.

To make sure you've got Internet connectivity now, issue this command: ping novell.com. You should get a response showing the IP address of Novell's server. If not, check your entries above and try again.

Activating WiFi on Startup. One last piece and we're finished. We obviously want to activate WiFi connectivity on bootup and, if you only have one WiFi access point and no neighbors like me, you shouldn't have to manually tweak your system thereafter. As we stated initially, this ain't your daddy's Windows or Mac machine, so where to put what isn't quite obvious. You're also going to need to do this in two boot cycles because there are two separate pieces. If the second piece works and the first one doesn't, you'll get a seg fault and crash every time. Do you need to ask how I know?

Step 1: While logged in as root, create the following new file: nano -w /etc/sysconfig/network-scripts/ifcfg-wlan0 using your IP address, netmask, and gateway settings from the netconfig drill above:


When you're finished adding the above commands, save the new file: Ctrl-X, Y, the press Enter. Now reboot your server: shutdown -r now. Once the system comes back up, log in as root, and issue the following command: ifconfig. Make sure that the display shows an IP address (inet addr) for your wlan0:

lo Link encap:Local Loopback
inet addr: Mask:
inet6 addr: ::1/128 Scope:Host
RX packets:425 errors:0 dropped:0 overruns:0 frame:0
TX packets:425 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:32582 (31.8 KiB) TX bytes:32582 (31.8 KiB)

wlan0 Link encap:Ethernet HWaddr 00:E0:98:F2:BB:40
inet addr: Bcast: Mask:
inet6 addr: fe80::2e0:98ff:fef2:bb40/64 Scope:Link
RX packets:976 errors:0 dropped:0 overruns:0 frame:0
TX packets:592 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:91331 (89.1 KiB) TX bytes:75930 (74.1 KiB)

Step 2: While logged in as root, edit the following file: nano -w /etc/rc.d/rc.local. The existing file should look like the following. You'll note that this is where Asterisk@Home is actually started on bootup so be careful with your typing.

# This script will be executed *after* all the other init scripts.
# You can put your own initialization stuff in here if you don't
# want to do the full Sys V style init stuff.

touch /var/lock/subsys/local
/usr/local/sbin/motd.sh > /etc/motd
/usr/sbin/amportal start

Above the touch line, add a couple of blank lines and then cut-and-paste the following code using your ESSID and the password of your wireless LAN:

/sbin/iwconfig wlan0 mode Auto > /dev/null
/sbin/iwconfig wlan0 essid "MundyLANd" > /dev/null
/sbin/iwconfig wlan0 key F57EC678F1B061BAC59EC593EFE > /dev/null
/sbin/iwconfig wlan0 mode Managed > /dev/null
/sbin/iwlist wlan0 scanning > /dev/null
/sbin/iwpriv wlan0 connect 01 > /dev/null

Leave the mode Auto line alone. On the essid line, enter the name of your WiFi LAN in quotes. If you're using WEP encryption on your wireless LAN, enter the hex key in the next line. Otherwise, just delete the line: Ctrl-K. Leave the mode Managed line as is. Leave the iwlist scanning and iwpriv lines the way they are. Now save your changes: Ctrl-X, Y, then press Enter. Reboot again: shutdown -r now. Log in as root. Then issue the following commands:

iwlist freq

The iwconfig command will tell you if you're connected to your Access Point and also indicate the Frequency (which tells you the channel your zd1211 is on). The iwlist freq decodes frequencies into channels and tells you which one you're talking on. If it's the same as the default channel on your access point, you're done. If it's not, run the command iwlist wlan0 scanning command again and eyeball the cell number which matches your access point. Then reset the channel by issuing the following command with the cell number you deciphered instead of 01: iwpriv wlan0 connect 01. Whew! Congratulations! You're now the proud owner of an Asterisk-based Voice Over Wi-Fi PBX, and you're getting darn close to being a Linux guru. Enjoy!

Free U.S. Calls. Everybody loves free samples so here's one for you. You may remember Gene Willingham and the good folks at TelaSIP, the winner and least expensive provider in our unlimited U.S. long distance calling shootout. In a moment of weakness, TelaSIP's agreed to let you try out some free U.S. phone calls on their nickel. The service uses our Asterisk server and TelaSIP's long distance bandwidth. Calls are limited to 10 minutes after which the callee will hear "Goodbye" followed by a click. You'll get two beeps followed by a fast busy. In other words, time's up! Here's how to use this free service. Call from a phone in the U.S. with CallerID. Call the number shown on the map (inset) which is one of our DIDs in Charleston, South Carolina. The call will never be answered so you won't be billed for the long distance call. Within 10 seconds, you should hear a fast busy. Hang up, and our Asterisk server will call you back within 30 seconds assuming you have caller ID enabled. You won't believe how many calls we receive each day from folks with caller ID disabled. HINT: No return call = No caller ID. If you do get a call back, listen carefully when you answer! You'll be provided a random password for your call, and then you'll be prompted to key it in. With your phone keypad, do that and press the pound key (#). If you get a message that it's incorrect, try again (HINT: We told you to listen carefully). Once you successfully enter the password, you'll then get a DISA dial tone. Dial 1 and then the area code and phone number of someone you love (in the United States only). This is an excellent way for you to check out the voice quality of TelaSIP calls without spending a dime. Just don't abuse the offer or this paragraph may magically disappear ... as will the free calls. For those that don't know us, we don't record your calls, and we don't store the number of the person you're calling although the Asterisk logs probably have it for a while anyway. For security purposes, we do log your CallerID and the time of your call just in case you do something you shouldn't be doing and the FBI traces the call back to us. If any of the above offends you, exercise your constitutional right to not use this free service. Believe it or not, someone wrote and asked why they couldn't use this service without CallerID enabled on their phone. Think about it! And you won't believe how many calls we receive each day with a CallerID of Asterisk. That won't work either.

Nerd Vittles Allison Fund. As we mentioned last week, our next major project is an Appointment Reminder System. Using a touchtone phone, you can schedule an unlimited number of customized voice reminders for delivery at any future time to any phone numbers you desire. To make it work, we need customized voice prompts for the IVR interface. Unfortunately, these cost money. Allison, who records the Asterisk voice prompts for Digium, needs to eat. And so do we. We're springing for the costs of the prompts up front, but this is your golden opportunity to contribute to the cause. Provided we raise enough money to cover the costs, we'll put the voice prompts in the public domain. Otherwise, when the project is presented, those that didn't contribute will have to record their own voice prompts in order to use the system. The generous will get the Allison prompts either on a password-protected web site or by email.

Last week's donations were a little disappointing. We raised a whopping $15 which means less than half of our regular readers have donated to the cause. And, until yesterday, there wasn't a single donor from the U.S. Thanks, Hollywood, for breaking the curse. Unless there's a surge of enthusiasm and generosity this week, better get those baritone voices tuned up. But, it's not too late to show your true colors! Go for broke and make a $5 non-tax-deductible contribution via PayPal using any major credit card. You'll sleep better! Just click on this link. And, you have our absolute commitment. If we hit a million bucks, we'll never pass the hat again. Of course, we might stop writing these silly articles, too. But, based upon last week's numbers, it doesn't look like there's much risk of a financial windfall here. We're just trying to recoup the costs of the voice prompts.

Coming Attractions. We have a number of projects underway to keep us busy for the next few weeks and months, but we always love to hear from you. If there is a particular Asterisk project you'd like us to cover down the road, leave a comment. We read every one of them. On our short list at the moment are a HOW-TO on connecting two Asterisk servers together and all the great things you can do once you've done that such as building a failover Asterisk system, HOW-TO connect remote IP and IAX phones to your Asterisk system (both wired and WiFi), instant messaging, key system emulation with Asterisk@Home 2.2, DUNDI, HOW-TO let Asterisk read your emails to you over the phone, the new Appointment Reminder System mentioned above, plus a few surprises. Don't expect all of this overnight, but we'll get there. With most of this stuff, we usually write about it as we build it. So you're reading these articles while riding in the front seat most of the time. Come back and visit often and tell your friends about us.

Some Recent Nerd Vittles Articles of Interest...


  1. 1. How much will all the Allison prompts cost?
    2. And what’s the ETA for the appointment reminder system?
    3. A how-to on getting Asterisk to behave like a key system would be a popular article (IMO).

    Keep up the good work!

    [WM: 1. Haven’t finished the code yet so I really don’t know. 2. I try not to get in the ETA game. Look how well Microsoft does at it, and they have a few more programmers than we do. I’m hoping in the next few weeks unless there’s a snag waiting in the wings. 3. Key system is on our radar. Thanks for the input.]

  2. Love the blog.

    Since starting to read your column – I have deployed 1 AAH server in the Washington DC area with extensions in Woodbridge (IAX) and Hawaii (SIP).

    Holding my breath for the AAH linkup howto.

    Change the donation link to allow adjustable donation amount – I’ll give more.

    Keep up the good work.

    [WM: Thanks for your note and generosity. We want to spread the burden fairly, but your offer is appreciated.]

  3. One Linux tool that you may not be aware of is Wifi Radar. It is a graphical tool for finding and connecting to preferred wireless networks. It is also a boot daemon to connect to the preferred profile automatically. That may save you a bit of manual work and not have to "issue dozens of unintelligible Linux commands to make a Wi-Fi adapter come to life".

    [WM: Good suggestion. I’ll try it out and report the results down the road.]

  4. FWIW, Centos and Asterisk@home supported wireless on my test machine out of the box (older Thinkpad Laptop with pcmcia wireless card), no fiddling required. And it works well with my home wireless WDS mesh set-up.

    There are a lot of advantages to redeploying a retired laptop for AAH – built-in battery (i.e. ups), pcmcia/wireless. Some (most old tp’s even have an option to add a 2nd hard disk in the bay that will permit image backups for upgrading to new aah versions without clobbering the old set-up.

    I’m not sure if it will put up with continuous use for years or has the horsepower much use beyond my limited requirements but it’s been working pretty well so far.

    [WM: Good to know and some great information to keep in mind. Linux does seem to have good built-in support for PCMCIA WiFi cards. It’s just the USB stuff that’s a real problem. Unfortunately, the USB dongles are the easiest to deploy … at least for desktop systems. Thanks.]

  5. Just found this yesterday and this is my new favorite asterisk site… donating shortly, I’m looking forward to the reminder system. Two things I would like to see… a revisit or more details on delivering voicemail to email (can’t get mine to work, it’s a linux problem, not an asterisk problem but still…) and a list (table of contents) of all the asterisk projects, so I don’t have to scroll through a huge page of them.

    [WM: There is a table of contents of sorts. Click on the link I’ve provided or click on the Asterisk Tutorials link in the upper right column. As for voicemail to email, take a look at the email section of the Asterisk@Home 2.2 Installation tutorial. There’s some additional information added in recent days.

  6. I was happy to make a donation.
    Some comments on that..
    You are certainly justified in asking for some money, Feel free to make the appeal more visually prominent and also to allow for more than $5.

  7. Thanks for all the great articles! As Asterisk@Home/CentOS gains popularity, it is no doubt becoming a fatter target. I would love to see another security article on how to work with the built in linux firewall iptables (or perhaps Shorewall) either manually or through WebMin.

  8. Thanks for all the great info on AAH which you have provided to date. One additional project that I would be interested in would be how to set up Asterisk@Home for paging both through a phone with speaker phone and an intercom system. This would be useful for Car dealerships, manufacturing plants etc.

    Thanks again for all wour efforts.


  9. It’d be cool to have asterisk integrate with zimbra so that you could click a contact number and your phone would ring. when you pick it up it would ring the contact number.

    [WM: I’m not familiar with zimbra, but we do exactly the same thing with our AsteriDex application which is free for the taking here.]

Comments are closed.