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The Switch can be configured as a global DHCP relay. This means that the Switch forwards all DHCP
requests from all domains to the same DHCP server. You can also configure the Switch to relay
DHCP information based on the VLAN membership of the DHCP clients.
43.4.1 DHCPv4 Relay Agent Information
The Switch can add information about the source of client DHCP requests that it relays to a DHCP
server by adding Relay Agent Information. This helps provide authentication about the source of
the requests. The DHCP server can then provide an IP address based on this information. Please
refer to RFC 3046 for more details.
The DHCP Relay Agent Information feature adds an Agent Information field (also known as the
Option 82 field) to DHCP requests. The Option 82 field is in the DHCP headers of client DHCP
request frames that the Switch relays to a DHCP server.
43.4.1.1 DHCPv4 Relay Agent Information Format
A DHCP Relay Agent Information option has the following format.
Table 203 DHCP Relay Agent Information Option Format
Code
(82)
i1, i2 and iN are DHCP relay agent sub-options, which contain additional information about the
DHCP client. You need to define at least one sub-option.
43.4.1.2 Sub-Option Format
There are two types of sub-option: "Agent Circuit ID Sub-option" and "Agent Remote ID Sub-
option". They have the following formats.
Table 204 DHCP Relay Agent Circuit ID Sub-option Format
SubOpt Code
1
(1 byte)
Table 205 DHCP Relay Agent Remote ID Sub-option Format
SubOpt Code
2
(1 byte)
The 1 in the first field identifies this as an Agent Circuit ID sub-option and 2 identifies this as an
Agent Remote ID sub-option. The next field specifies the length of the field.
43.4.2 DHCPv4 Option 82 Profile
Use this screen to create DHCPv4 option 82 profiles. Click IP Application > DHCP > DHCPv4 in
the navigation panel and click the Option 82 Profile link to display the screen as shown.
Chapter 43 DHCP
Length
i1
(N)
Length
N
Slot ID, Port ID, VLAN ID, System Name or String
(1 byte)
Length
N
MAC Address or String
(1 byte)
GS3700/XGS3700 Series User's Guide
i2
iN
...
Value
Value
416
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