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Chapter 41 DHCP
XGS-4526/4528F/4728F User’s Guide
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41.4 DHCP Relay
Configure DHCP relay on the Switch if the DHCP clients and the DHCP server are
not in the same broadcast domain. During the initial IP address leasing, the
Switch helps to relay network information (such as the IP address and subnet
mask) between a DHCP client and a DHCP server. Once the DHCP client obtains an
IP address and can connect to the network, network information renewal is done
between the DHCP client and the DHCP server without the help of the Switch.
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.
41.4.1 DHCP 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 to
the Option 82 field. 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 information that the Switch sends to the
DHCP server:
Table 132 Relay Agent Information
FIELD LABELS DESCRIPTION
Slot ID (1 byte) This value is always 0 for stand-alone switches.
Port ID (1 byte) This is the port that the DHCP client is connected to.
VLAN ID (2 bytes) This is the VLAN that the port belongs to.
Information (up to 64 bytes) This optional, read-only field is set according to
system name set in Basic Settings > General Setup.