Protocols And Standards - 3Com Switch 4800G 24-Port Configuration Manual

796 C 56: DHCP O
HAPTER
Protocols and
Standards
VERVIEW
2 Verbose padding format:
The padding contents for sub-options in the verbose padding format are:
sub-option 1: Padded with the user-specified access node identifier (ID of the
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device that adds Option 82 in DHCP messages), and type, number, and VLAN
ID of the port that received the client's request. Its format is shown in the
following figure.
Figure 245 Sub-option 1 in verbose padding format
Sub-option type (0x01)
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In the above figure, except that the VLAN ID field has a fixed length of 2 bytes, all
the other padding contents of sub-option 1 are length variable.
sub-option 2: Padded with the MAC address of the interface that received the
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client's request. It has the same format as that in normal padding format, as
shown in Figure 244.
Option 184
Option 184 is a reserved option, and parameters in the option can be defined as
needed. The device supports Option 184 carrying the 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 is a
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server serving as the network calling control source and providing program
downloads.
Sub-option 2: IP address of the backup network calling processor that DHCP
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clients will contact when the primary one is unreachable.
Sub-option 3: Voice VLAN ID and the result whether DHCP clients take this ID
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as the voice VLAN or not.
Sub-option 4: Failover route that specifies the destination IP address and the
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called number (SIP users use such IP addresses and numbers to communicate
with each other) that a SIP user uses to reach another SIP user when both the
primary and backup calling processors are unreachable.
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You must define the sub-option 1 to make other sub-options take effect.
RFC2131: Dynamic Host Configuration Protocol
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RFC2132: DHCP Options and BOOTP Vendor Extensions
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RFC1542: Clarifications and Extensions for the Bootstrap Protocol
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RFC 3046: DHCP Relay Agent Information Option
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Length
Port type
VLAN ID
Node identifier
Port number