The Cisco 7911 is not a native SIP phone. The Cisco 7911 is a Unified IP Phone for use with Cisco's propriety UC service and come with SCCP firmware installed out of the box. There is SIP firmware available, but it has it's limitations and you will still need to configure it by pushing the required XML configuration files to the phone.
Some things to note:
- You only need to flash the SIP firmware if your phone has the SCCP firmware installed.
- You will need a TFTP server
- You will need to create and upload the various configuration files to the phone via TFTP
To be honest, you're better off throwing the Cisco 7911 in the trash. Replace it with a true SIP based VoIP phone. These have a built in WEB GUI that you configure just like you would a WiFi router. You can pick them up on eBay for around £15 and up...
*I am not affiliated with eBay or the sellers and I am not earning any commission.
- Snom 320 (£17.99)
- Cisco SPA504G (£16.99)
- Yealink T21P (£16.89)
Anyway, if you still want to go ahead and setup the the Cisco 7911 then you need SIP firmware 9.4.(2)SR3 and the following configuration files: apps11.9-4-2ES26.sbn, cnu11.9-4-2ES26.sbn, cvm11sip.9-4-2ES26.sbn, dialplan.xml, dsp11.9-4-2ES26.sbn, jar11sip.9-4-2ES26.sbn, SEP[MAC].cnf.xml, SIP11.9-4-2SR3-1S.loads, term06.default.loads, term11.default.loads and XMLDefault.cnf.xml.
Easiest method is to follow the guide here