Dhcpv4 Relay Agent Information - ZyXEL Communications GS2210 Series User Manual

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.

40.4.1 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.
Relay Agent Information can include the System Name of the Switch if you select this option.
You can change the System Name in Basic Settings > General Setup.
The following describes the DHCP relay agent information that the Switch sends to the DHCP
server:
Table 165 Relay Agent Information
FIELD LABELS
Slot ID
Port ID
VLAN ID
Information
40.4.1.1 DHCPv4 Relay Agent Information Format
A DHCP Relay Agent Information option has the following format.
Table 166 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.
40.4.1.2 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 167 DHCP Relay Agent Circuit ID Sub-option Format
SubOpt Code
1
(1 byte)
Chapter 40 DHCP
DESCRIPTION
(1 byte) This value is always 0 for stand-alone switches.
(1 byte) This is the port that the DHCP client is connected to.
(2 bytes) This is the VLAN that the port belongs to.
(up to 64 bytes) This optional, read-only field is set according to system name set in
Basic Settings > General Setup.
Length i1
(N)
Length
N Slot ID, Port ID, VLAN ID, System Name or String
(1 byte)
GS2210 Series User's Guide
i2 iN
...
Value
339