Here is the setup.. my company has inherited a bunch of Cisco VOIP phone, it would be a waste to toss them, and they are pretty interesting to play with. If you don’t know how these work I’ll give you a quick overview. They are a bit of a pain, but it’s not too par for the course from at least some other models of phone (for example, from avaya) and understand this description is from a Network Engineer, who doesn’t have any real experience with VOIP outside of that of someone who understands the basics. Anyhow.. this is how they work. In the Cisco World, you use Call Manager, and each phone runs on either SIP, SCCP or some weird thing called MCGP, which isn’t terribly common so I hear. SCCP is sometimes called Skinny.
Each of these model phones (7940, 7960, and 7942’s, are the ones we have.) reaches out to a TFTP server someplace and downloads some configuration files to essentially tell it, what firmware to run, what server to use, and what it’s credential info is to essentially be the phone you are expecting it to be. You can (in my case) specify this TFTP server as an option on your DHCP server should you have one, or you can go through a very complicated process to set this manually on phone. But you must at the very least have a TFTP server, and it’s fine for it to run on your Asterisk Server.
Asterisk, if you are unfamiliar, is an open source VOIP PBX. You can use Asterisk to connect many things, even other Asterisk servers. Some distributions of Asterisk combine other Applications like Chat and Email, but they are clearly not the main attraction. I chose AsteriskNOW, but did try Elastix.
Cisco 7940 & 7960, I also have a few ATA186’s and some of these extra line extenders for the 7960 which I have not played with yet.
Cisco 7942 * <-- had issues getting good config files going for this model, so if the google has brought you here, I have no answers yet. I'll have to resolve this someday because I may have about 30 of these and I'm not throwing them away, or using call manager.
The switch: I have at my disposal a 48 port Cisco Catalyst 3560 POE switch. I have wiped it's config and it's unremarkable. This is a 100mb switch, and other than the POE isn't terrible useful to my work, as we prefer HP switches. I have read that it's possible that the 7940 / 7960 don't like gettng power from any other POE than a cisco switch, but I have not tested this. I do have some injectors which I can try to use to test.
The Server: A 8 year PC with 2gb of ram, and a Pentium 4HT processor. I have a 120GB hard drive in this. This is all the storage I have for Voicemail on the system also.
I do run DHCP on another server in my LAN, it's debian, and the only thing special I did there was set this line in the DHCP config in /etc/dhcp/dhcpd.conf adding:
option tftp-server-name “192.168.2.22”;
In the next part I’ll go over what to setup on the Asterisk NOW server, and give you some example configs for some 7940 phones.