H3C Technologies H3C S10500 Series Switches - Manual (Page 45)

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2. Verbose padding format
• Sub-option 1: Padded with the user-specified access node identifier (ID of the device that adds
Option 82 in DHCP messages), and the type, number, and VLAN ID of the interface that received
the client’s request.
Figure 25 Sub-option 1 in verbose padding format
NOTE:
The VLAN ID field has a fixed length of 2 bytes. All the other padding contents of sub-option 1 are length
variable. See
Figure 25 .
• Sub-option 2: Padded with the MAC address of the DHCP relay agent interface or the MAC
address of the DHCP snooping device that received the client’s request. It has the same format as
that in normal padding format. See Figure 24 .
Option 184
Option 184 is a reserved option, and parameters in the option can be defined as needed. The device
supports Option 184 carrying voice related parameters, so a DHCP client with voice functions can get an
IP address along with specified voice parameters from the DHCP server.
Option 184 involves the following sub-options:
• Sub-option 1: IP address of the primary network calling processor, which serves as the network
calling control source and provides program downloads.
• Sub-option 2: IP address of the backup network calling processor. DHCP clients contact the backup
when the primary is unreachable.
• Sub-option 3: Voice VLAN ID and the result whether or not DHCP clients take this ID as the voice
VLAN.
• Sub-option 4: Failover route that specifies the destination IP address and the called number. A
Session Initiation Protocol (SIP) user uses this IP address and number to reach another SIP user when
both the primary and backup calling processors are unreachable.
NOTE:
For Option 184, you must define sub-option 1 to make other sub-options take effect.
Protocols and standards
• RFC 2131, Dynamic Host Configuration Protocol
• RFC 2132, DHCP Options and BOOTP Vendor Extensions
• RFC 1542, Clarifications and Extensions for the Bootstrap Protocol
• RFC 3046, DHCP Relay Agent Information Option
• RFC 3442, The Classless Static Route Option for Dynamic Host Configuration Protocol (DHCP)
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