Protocols and Standards 571Figure 169 Sub-option 1 in verbose padding formatn In the above figure, except that the VLAN ID field has a fixed length of 2 bytes, allthe other padding contents of sub-option 1 are length variable.■ sub-option 2: Padded with the MAC address of the interface that received theclient’s request. It has the same format as that in normal padding format, asshown in Figure 168.Option 184Option 184 is a reserved option, and parameters in the option can be defined asneeded. The device supports Option 184 carrying the voice related parameters, soa DHCP client with voice functions can get an IP address along with specified voiceparameters from the DHCP server.Option 184 involves the following sub-options:■ Sub-option 1: IP address of the primary network calling processor, which is aserver serving as the network calling control source and providing programdownloads.■ Sub-option 2: IP address of the backup network calling processor that DHCPclients will contact when the primary one is unreachable.■ Sub-option 3: Voice VLAN ID and the result whether DHCP clients take this IDas the voice VLAN or not.■ Sub-option 4: Failover route that specifies the destination IP address and thecalled number (SIP users use such IP addresses and numbers to communicatewith each other) that a SIP user uses to reach another SIP user when both theprimary and backup calling processors are unreachable.n You must define sub-option 1 to make other sub-options take effect.Protocols andStandards■ RFC2131:Dynamic Host Configuration Protocol■ RFC2132:DHCP Options and BOOTP Vendor Extensions■ RFC1542:Clarifications and Extensions for the Bootstrap ProtocolSub-option type (0x01) Length Node identifierInterface type Interface numberPVC identifier VLAN ID
