Phones - How Digium phones prioritize boot configuration options?
Within our Digium Phone product line, there are four ways that System Administrator may direct the phone to download or use its configuration in order to connect to the PBX and these are:
Phone internal configuration. (*1)
mDNS / Avahi.
DHCP Boot Option 66.
Manually point the phone to a configuration server
(*1): The phone internal configuration is not a user selectable option per-se, but rather a previous configuration that was done either manually by the System Administrator or previous download from a configuration server, we are adding this as option since its used by the phone in order to determine what to do with any available boot server option
The Digium phones will use the following rules
If a phone has been previously configured, the phone will use its internal configuration to contact the PBX, the phone will ignore any Avahi/mDNS or DCHP boot option 66 that may be available on the network
If the phone does not have a configuration or has recently been factory defaulted, if Avahi / mDNS or DHCP Boot Option 66 exclusively – not both at the same time – the phone will use either of the available options to contact the configuration server
If the phone does not have a configuration or has recently been factory defaulted, if Avahi / mDNS and DHCP Boot Option 66 are available at the same time, the phone will require user intervention and it will wait for the user to select which option the phone should use in order to contact the configuration server.
If the phone does not have a configuration or has recently been factory defaulted, and Avahi / mDNS reports that there is more than one configuration server, the phone will required the user to manually select the configuration server that the phone needs to connect.
If the phone does not have a configuration or has recently been factory defaulted and Avahi / mDNS and DHCP are not available, the phone will require that the user manually point the phone to its configuration server.
Network configuration recommendations
If you are planning your network we suggest that it is implemented like this:
In the network that your PBX is located.
Do not use DHCP boot option 66, this is because Switchvox and Asterisk with DPMA already have implemented Avahi / mDNS and it will advertise the configuration server by itself, DHCP boot option 66 may lead to a situation in which the phone will require user action to select the correct option if the phone is factory defaulted.
In other networks that your PBX is not located.
You can use DHCP boot option 66 or Avahi / mDNS - but not both at the same time – and the reason is similar to the previous recommendation, you want to only leave one option so the phones automatically select it and connect to the configuration server without user action.
Additional resources
If you need additional information on how to setup DHCP Boot Option 66 or Avahi / mDNS we suggest to read:Digium Phone Provisioning