Voice over IP (VoIP) VoIP System Telephones
5. From Status, select the address assignment option. Confirm with Apply. The
DHCP Server page is re-displayed.
6. Add the configured VoIP system telephones to the list of IP addresses. Click on the New button.
7. Enter the VoIP system telephone’s IP address and MAC address. Enter the IP address reserved by the DHCP service program. Confirm with Apply.
Restart the OpenCom 107 and all connected VoIP system telephones.
8.4.4 Start Procedure
It may sometimes be useful to understand a VoIP system telephone’s start procedure. Examples:
■ A complex DHCP address assignment prevents the operation of the
OpenCom 107’s DHCP server within the LAN.
■ A VoIP system should be operated with a non-broadcast-capable IP connection. This may be an RAS connection, a VPN connection or another type of routed connection.
An external DHCP server can also control a VoIP system telephone’s start procedure. In this case, system software matching the type of VoIP system telephone must be transferred via TFTP.
After the VoIP system telephone has been connected to the mains power supply, the start procedure is as follows:
1. The boot loader starts and shows the VoIP system telephone’s MAC address in the display. A DHCP request is sent simultaneously via broadcast on the
255.255.255.255 broadcast address.
2. An IP address, network mask and the default gateway for the start procedure are sent from the DHCP server. Via the “Next server” option, the DHCP server also provides the TFTP server’s IP address and the operations software’s file name. The DHCP server uses the MAC address to select the operations software file which matches the type of device.
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Voice over IP (VoIP) VoIP System Telephones
3. The boot loader loads the operations software file from the specified TFTP server. The TFTP server’s IP address and the file’s name are shown in the display.
The loaded operations software is started.
4. The operations software sends a DHCP request on the broadcast address
255.255.255.255. The VoIP system telephone now receives an IP address, network mask and default gateway for operations from the DHCP server. Using
“Option 43”, which is reserved for this purpose, the DHCP server also provides the IP address of the communication system and port number 8100 for registration.
5. The VoIP system telephone creates a TCP connection to the supplied IPaddress/port-number combination and sends a registration query. The
OpenCom 107 checks the MAC address sent with the registration and confirms the registration request if the VoIP system telephone is listed in the menu
PBX Configuration: Devices: VoIP Phones. The keep-alive time, port number
(8101) for telephony signalling and the value to use for the TOS byte are also communicated in the registration answer.
6. The VoIP system telephone creates a second TCP connection using the signalling port number 8101 and sends a registration analogue to the U pn
system telephones.
7. Extra connections are created using the IP protocol RTP (“Realtime Transport
Protocol”) for call data when a call is created. For calls between two VoIP system telephones, port numbers above 8200 are used. For transmission to a Media
Gateway card, a port in the range 1024 – 1087 is used.
If you wish to operate a VoIP system telephone via a routed IP connection (for example VPN or RAS) it may be necessary to configure an external DHCP server accordingly. Please note the selection of the codec and keep-alive time for RAS connections. This can be done by selecting the default profile RAS in the
PBX Configuration: Devices: VoIP Phones for the VoIP system telephone. The operations software provided via TFTP must match the type of device and communication system. You may also need to configure BOOTP, DHCP and TFTP servers for the VoIP system telephone.
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