IP Phone 7821 registering to SRST

[KarolineSoares76078]

Hi there.

I have a 7821 device on Call Manager 12.0 that is registering directly with SRST.
Firmware version: sip78xx.12-0-1-11

In the status messages I can see the "DNS Timeout" so I checked the configuration in Voice DHCP and there is a configured domain. Other devices on the same network can resolve DNS with the domain of this configuration,
but they are of different models.
On the device's web page, I have configured Unified CM1-hostname / CM2-hostname / CM3- CUCM IP / CM4- SRST IP (this is what is always active). If it doesn't solve DNS problems but can register with SRST, I wonder why it can't register with Call Manager by IP (which is in Unified CM3).

I tried to delete the ITL file and factory reset but it did not work. I know that for DNS problems the best thing is to configure a domain in DHCP, however this configuration was already applied and the problems still persist.

Do you have any tips on what to do or what to search for?

[davisjaron]

Instead of manually configuring TFTP and SRST on the phone, configure everything in CUCM, and then give your Voice DHCP option 150 and point it towards your CUCM with TFTP running.  When the phone gets an IP address, it will get the option 150 with it, and it will reach out to CUCM for all of it's configurations, including CUCM and SRST. 

I'm thinking it's possible that your phone can't get to CUCM for some reason.  Perhaps a firewall is blocking port 6970 between the phone and CUCM, which is your TCP TFTP port.  If this changed recently, it wouldn't affect your current phones functionally because they're already registered, but it would prevent new phones from downloading a configuration.

Look into that, and then post the phone logs if you can't figure it out after that.