A CONFIGURING OPTION 184 ON AW INDOWS 2000 DHCP S ERVEROverview RFC 2132 (DHCP Options and BOOTP Vendor Extensions) allows forvendor-specific extensions to the DHCP protocol. It defines that optioncodes in the range 128 through 254 are set aside for vendor-specificextensions.3Com telephones can receive their IP configuration from a DHCP server.However, 3Com telephones need configuration information that is notpart of a standard DHCP response. You can use DHCP option 184 tospecify this extended information:■ NCP IP Address — Each telephone must receive a download ofoperating settings from the VCX Downloader task, which typicallyresides on the VCX Call Processing Server.■ Alternate Server IP Address — Specifies a second location fromwhich a telephone can receive its download. Typically, this is the IPaddress of the Secondary VCX Call Processing Server in a dual-serverconfiguration.■ Voice VLAN Configuration — If you configure any of your 3Comtelephones or your VCX system on Virtual LANs, you can configureyour DHCP server to specify VLAN ID numbers for each scope. You canalso enable and disable VLAN operation for each DHCP scope.■ Fail-Over Call Route Point — You can define a single fail-over routepoint (IP address) and an associated dial string for SIP devices such astelephones to use.If a failure occurs on the Primary VCX Call Processing Server, thetelephone switches to the Secondary VCX Call Processing Server. Ifboth are unavailable, the telephone switches to peer-to-peer SIPoperation and attempts to connect to the IP address of the fail-overroute point. The dial string controls the types of calls that can be madewhile the telephone is in peer-to-peer mode.
