3com 8807 사용자 가이드
702
C
HAPTER
57: DHCP C
ONFIGURATION
[3Com-Vlan-interface2]ip relay address 202.38.1.2
n
Besides the above configurations for DHCP Relay, you need to configure address
pool on the DHCP server and make sure the DHCP server and the switch interface
connecting the two DHCP clients is routing reachable with each other.
pool on the DHCP server and make sure the DHCP server and the switch interface
connecting the two DHCP clients is routing reachable with each other.
c
CAUTION: Do not change or delete the IP address of the interface corresponding
to the DHCP Relay; otherwise users will be unable to obtain IP addresses to access
the Internet.
to the DHCP Relay; otherwise users will be unable to obtain IP addresses to access
the Internet.
DHCP Option 82
Configuration
Configuration
Introduction to Option
82 Support on DHCP
Relay
Option 82 is the relay agent information option in the DHCP packets. When a
DHCP client sends a DHCP request packet and the packet must be forwarded by a
DHCP relay to reach a DHCP server, if Option 82 support is enabled on the DHCP
relay, the DHCP relay adds Option 82 into the request packet. Option 82 can be
composed of many sub-options, but Option 82 mentioned in this chapter only
supports sub-option 1, sub-option 2 and sub-option 5. Sub-option 1 defines the
agent circuit ID (that is, Circuit ID), and sub-option 2 defines the agent remote ID
(that is, Remote ID). sub-option 5 is the subitem of link selection, which includes
the IP address that the DHCP Relay adds.
DHCP client sends a DHCP request packet and the packet must be forwarded by a
DHCP relay to reach a DHCP server, if Option 82 support is enabled on the DHCP
relay, the DHCP relay adds Option 82 into the request packet. Option 82 can be
composed of many sub-options, but Option 82 mentioned in this chapter only
supports sub-option 1, sub-option 2 and sub-option 5. Sub-option 1 defines the
agent circuit ID (that is, Circuit ID), and sub-option 2 defines the agent remote ID
(that is, Remote ID). sub-option 5 is the subitem of link selection, which includes
the IP address that the DHCP Relay adds.
With Option 82, the information about the addresses of the DHCP clients and the
DHCP relay devices can be recorded on the DHCP server. Using Option 82 together
with other software can implement the DHCP allocation restrictions and the
accounting function.
DHCP relay devices can be recorded on the DHCP server. Using Option 82 together
with other software can implement the DHCP allocation restrictions and the
accounting function.
Concepts
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Option
A DHCP packet has a field called options, which contains part of the lease
information and the packet type. The options field is length-variable and consists
of one option at least and 255 options at most.
information and the packet type. The options field is length-variable and consists
of one option at least and 255 options at most.
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Option 82
Option 82 is also called relay agent information option and is a part of the options
field in a DHCP packet. Option 82 is defined in RFC 3046 before Option 255 and
behind other options. You can define a minimum of one sub-option and a
maximum of 255 sub-options for Option 82. At present, the commonly used
sub-options in Option 82 include sub-option 1, sub-option 2 and sub-option 5.
field in a DHCP packet. Option 82 is defined in RFC 3046 before Option 255 and
behind other options. You can define a minimum of one sub-option and a
maximum of 255 sub-options for Option 82. At present, the commonly used
sub-options in Option 82 include sub-option 1, sub-option 2 and sub-option 5.
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sub-option 1
Sub-option 1 belongs to Option 82 and defines the Circuit ID. Usually configured
on the DHCP relay devices, it indicates that the forwarded packets will carry the
VLAN ID and Layer 2 port number of the port of the switch that the DHCP client is
connected to. Generally, sub-option 1 and sub-option 2 are used together to
identify a DHCP client.
on the DHCP relay devices, it indicates that the forwarded packets will carry the
VLAN ID and Layer 2 port number of the port of the switch that the DHCP client is
connected to. Generally, sub-option 1 and sub-option 2 are used together to
identify a DHCP client.
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Sub-option 2