System > Dhcp Auto Configuration; System > Dhcp Relay > Dhcp Relay Global Settings - D-Link DGS-1210 Series Manual

4 Web-based Switch Configuration
This page contains the entries of DNS dynamic hosts.
System > DHCP Auto Configuration
DHCP Auto Configuration is a feature that helps user to download the designated configuration file via TFTP
protocol automatically. When enabled, the Switch becomes a DHCP client and gets the configuration file
from a TFTP server on next boot up. To accomplish this, the DHCP server must deliver the TFTP server IP
address and configuration file name information in the DHCP options. The TFTP server must be up and
running and store the necessary configuration file in its base directory when the request is received from the
Switch.
System > DHCP Relay > DHCP Relay Global Settings
DHCP relay is a feature that helps user to assign host IPs across the LANs. Switch acts as a relay agent
when function enabled.
DHCP Relay State: Globally Enable/Disable DHCP relay function by selecting from drop-down list. The
default value is Disabled.
DHCP Relay Hops Count Limit (1-16): This field allows an entry between 1 and 16 to define the maximum
number of router hops DHCP messages can be forwarded across. The default hop count is 4.
DHCP Relay Time Threshold (0-65535): Allows an entry between 0 and 65535 seconds, and defines the
maximum time limit for routing a DHCP packet. If a value of 0 is entered, the Switch will not process the
value in the seconds field of the DHCP packet. If a non-zero value is entered, the Switch will use that value,
along with the hop count to determine whether to forward a given DHCP packet.
DHCP Relay Agent Information Option 82 State: This field can be toggled between Enabled and Disabled
using the pull-down menu. It is used to enable or disable the DHCP Agent Information Option 82 on the
Switch. The default is Disabled.
Enabled – When this field is toggled to Enabled the relay agent will insert and remove DHCP relay
information (option 82 field) in messages between DHCP servers and clients. When the relay agent
receives the DHCP request, it adds the option 82 information, and the IP address of the relay agent
(if the relay agent is configured), to the packet. Once the option 82 information has been added to
the packet it is sent on to the DHCP server. When the DHCP server receives the packet, if the server
is capable of option 82, it can implement policies like restricting the number of IP addresses that can
be assigned to a single remote ID or circuit ID. Then the DHCP server echoes the option 82 field in
the DHCP reply. The DHCP server unicasts reply to the back to the relay agent if the request was
relayed to the server by the relay agent. The switch verifies that it originally inserted the option 82
data. Finally, the relay agent removes the option 82 field and forwards the packet to the switch port
that connects to the DHCP client that sent the DHCP request.
Figure 4.35 – System > DHCP Auto Configuration
Figure 4.36 – System > DHCP Relay > DHCP Relay Global Settings
D-Link Smart Managed Switch User Manual
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