here are some known issues with some Cisco managed Switches having Smartports that can cause CyberData Devices to have issues.
The SF/SG 200 and SF/SG 300 Series Managed Switches and some other Cisco switches have a smartport configuration that may cause Digium phones and CyberData devices to unregister and to timeout during SIP Registration.
Symptoms: Phones in the data network going into error mode and unreachable, the devices not able to register or reconnect with the cloud service even if the user rebooted it.
References: According to traces and logs from the firewall, devices were having some timeout issues and were not able to establish connection.
Found several references at the Digium Web Site KB page and blogs.
We found there were issues with Cisco SFP switches and apply the changes suggested.
In addition to that, we also contacted CISCO for additional advice regarding the problem, they requested as information about how the ASA55XX was defined between outside/inside interfaces and provided information about ARP proxy and behavior of device.
Some links about this provided:
Per Digium KB
Disable CDP from smartports on SFPX00 devices and test
Retest Digium phones and see if they can connect, if they cannot try disabling smartports and test again.