I finally figured out the problem with the phones when I was waiting for my train last night- it turned out it wasn?t actually anything to do with SIP. The way things had gone led me down that path and I needed to get away from the office before I could think straight about it.

I?d added the phones as SCCP with autoregistration. I then tried to add a SIP phone manually but this failed. It took the SIP firmware okay but was coming up as ?Registration Rejected.? I thought I had maybe misconfigured authentication or something so the next thing I tried was to autoregister the phones with SIP. SIP autoregistration came up as ?Registration Rejected? as well though. This had me thinking that there was something wrong with SIP phones registering, maybe a configuration issue or missing parameter. It was something a lot more simple though- I?d configured the autoregistration range for existing phones and the directory numbers had been taken when the phones registered with SCCP. When I deleted the SCCP phones their directory numbers were still in the system, so there were no numbers available when they tried to autoregister with SIP.

When I came in this morning I deleted the DN?s from the system and SIP autoregistration worked fine. I also added a SIP phone manually this morning. I?m not sure why I couldn?t do that last night as I double-checked the MAC address was correct. I?m still not sure what the problem was there but never mind everything?s working fine now.