Option 176 is used for legacy IP Office phones (4600 and 5600 series phones). Option 242 is used for 1600 and 9600 series phones. The DHCP option provides the IP Office address, the H.323 port number, the TFTP or HTTP server used, and (optionally) VLAN information.
The options look like this:
OPTION 176 MCIPADD=xxx.xxx.xxx.xxx,MCIPORT=yyyy,TFTPSERVER=zzz.zzz.zzz.zzz
OPTION 242 MCIPADD=xxx.xxx.xxx.xxx,MCIPORT=yyyy,HTTPSERVER=zzz.zzz.zzz.zzz
xxx.xxx.xxx.xxx is the IP Address of your IP Office that the phones will use for registration, and yyyy is the port number (almost always 1719). The TFTP or HTTP server address is almost always the same as the IP Office address, however some deployments may use an external server to support additional simultaneous connections.
In a scenario where you have multiple servers in a resilient environment you can have multiple entries for MCIPADD - simply separate them with a comma:
OPTION 242 MCIPADD=192.168.42.1,192.168.42.2,MCIPORT=1719,HTTPSERVER=192.168.42.1,192.168.42.2With Option 242 you can specify a folder on the HTTP server that contains the files needed by the IP Phone using the HTTPDIR=path_to/files.
Keep in mind that there is a limit of 127 characters in a DHCP Offer. If the scope would exceed this you can use OPTION 66 to specify the TFTP Server for Option 176.
When using VLANs to separate voice and data traffic you need to ensure that the VLAN details are specified in the default VLAN:
L2Q=1 enables VLAN tagging.
L2QVLAN=xxx where xxx is the VLAN ID for your voice VLAN.
In this scenario you would have your options as follows:
Default DHCP Offer:
OPTION 242 L2Q=1,L2QVLAN=200Voice VLAN DHCP Offer:
OPTION 242 MCIPADD=192.168.42.1,MCIPORT=1719,HTTPSERVER=192.168.42.1The IP Phones will pick up their VLAN from the default offer then request a new DHCP scope in the correct VLAN, at which point they will receive their configuration from the voice VLAN.