Chapter 35 DHCP
GS1920 Series User’s Guide
282
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.
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:
35.2 DHCP Configuration
Click IP Application > DHCP in the navigation panel to display the screen as shown. Click the link
next to DHCPv4 to open screens where you can enable and configure DHCPv4 relay settings and
create option 82 profiles. Click the link next to DHCPv6 to open a screen where you can configure
DHCPv6 relay settings.
Figure 205
IP Application > DHCP
Table 136
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.
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