This implies that the only thing to do is actually to run the DHCP server. Automatic configuration of scopes By default, the DHCP server works in the mode of automatic configuration of scopes. For SIP the inspection is to be disabled, but the HTTP-Proxy/Content Filter rules may affect the connection to 3CX Phone System for updates and My Phone connections (not part of this document). The status of this type of firewall is: Supported Nat Type: IP Restricted Firewall configuration will never be carried out by the 3CX Staff, and must be made by the System Administrator of the company. This is mainly due to the behavior of the firewall expecting audio/data to be send before it allows receiving on dynamically created NATs. Based on the timing, it could happen that the 3CX Phone System sends audio to the remote IP Phone’s IP: RTPport address, before the STUNed IP Phone has send data to the 3CX Phone System.
NOTE DHCP protocol enables adding several optional parameters, such as: 015: Domain name — local Internet domain (not to be used for specification of Windows NT domain name). Using the Remove button you can release the selected IP address and/or cancel IP address reservation on the spot. DHCPRELEASE control message will be sent to the corresponding client. If an IP address is to be kept, the client must request an extension on the period of time before the lease expires. If the client has not required an extension on the lease time, the IP address is considered free and can be assigned to another client. So called reservations can be also defined on the DHCP server — certain clients will have their own IP addresses reserved. In general Kerio Control is known to work correctly and can be used as a gateway in front of a 3CX Phone System to connect Vo IP Providers, Direct Remote Extensions (STUN) and 3CX Tunnel connections.