The full configuration of dnsmasq it’s out of scope for this doc, but in a nutshell you need these in your dnsmasq config: Usually Cisco require a valid support contract before you can download anything useful from their website, but it seems that since these phones are now out of support they have offered up the firmware free of charge.
You do still need to register an account to download the files. Go here: https://software.cisco.com/download/type.html? mdfid=280083379&catid=280789323 Follow the link to the SIP software.
From here you have two types of locales that can exist, system-defined locales which are produced by cisco, and user-defined which are custom, now for the purpose of the CCIE Voice I am only really concerned about system-defined locales (i.e.
While I can tell you that Cisco recommends using SIP firmware 8.3.2 SR1S, I cannot provide the firmware files because of their licensing agreements.
Assuming you can get the correct firmware copied to your tftp server, and your DHCP server is serving out Option 66 to tell the phones where to look for its config files (yes, these are mandatory requirements), then we can get into how to actually configure the phones themselves.
Anyone who has had the “pleasure” of trying to configure a Cisco 7975 phone with a SIP IP PBX system such as Asterisk, trixbox, or 3CX can attest to the fact that the phones are very picky with their config files and much of the information that is really handy to know is simply not documented anywhere.
On top of that, to get the phones to even work right you have to use very specific versions of the SIP firmware as the phones are not designed to work with third-party phone systems that talk generic SIP messages.