TP-Link Jetstream TL-SL2428P - Dhcp; Overview; Supported Features

User Guide 396
Configuring DHCP Service DHCP
1
DHCP
1.1 Overview
DHCP (Dynamic Host Configuration Protocol) is widely used to automatically assign IP
addresses and other network configuration parameters to network devices, enhancing the
utilization of IP address.
1.2 Supported Features
The supported DHCP features of the switch include DHCP Relay and DHCP L2 Relay.
DHCP Relay
DHCP Relay is used to process and forward DHCP packets between different subnets or
VLANs.
DHCP clients broadcast DHCP request packets to require for IP addresses. Without this
function, clients cannot obtain IP addresses from a DHCP server in the different LAN
because the broadcast packets can be transmitted only in the same LAN. To equip each
LAN with a DHCP server can solve this problem, but the costs of network construction will
be increased and the management of central network will become inconvenient.
A device with DHCP Relay function is a better choice. It acts as a relay agent and can
forward DHCP packets between DHCP clients and DHCP servers in different LANs.
Therefore, DHCP clients in different LANs can share one DHCP server.
DHCP Relay includes three features: Option 82 and DHCP VLAN Relay.
■ Option 82
Option 82 is called the DHCP Relay Agent Information Option. It provides additional security
and a more flexible way to allocate network addresses compared with the traditional DHCP.
When enabled, the DHCP relay agent can inform the DHCP server of some specified
information of clients by inserting an Option 82 payload to DHCP request packets before
forwarding them to the DHCP server, so that the DHCP server can distribute the IP
addresses or other parameters to clients based on the payload. In this way, Option 82
prevents DHCP client requests from untrusted sources. Besides, it allows the DHCP server
to assign IP addresses of different address pools to clients in different groups.
An Option 82 has two sub-options, namely, the Agent Circuit ID and Agent Remote ID.
The information that the two sub-options carry depends on the settings of the DHCP
relay agent, and are different among devices from different vendors. To allocate network
addresses using Option 82, you need to define the two sub-options on the DHCP relay
agent, and create a DHCP class on the DHCP server to identify the Option 82 payload.
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