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Chapter 64 DHCP
XS3800-28 User’s Guide
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64.3 DHCPv4 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.
64.3.1 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 SYSTEM > General Setup .
The following describes the DHCP relay agent information that the Switch sends to the DHCP server:
VID This field displays the ID number of the VLAN for which the Switch acts as a DHCP relay agent.
Current
Source
Address
This field displays the source IP address of the DHCP requests that the Switch forwards to a DHCP
server.
Table 234 NETWORKING > DHCP > DHCPv4 Relay > DHCP Relay Status
LABEL DESCRIPTION
Table 235 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
SYSTEM > General Setup .