ZyXEL Communications OLT2406, User Manual

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OLT2406 User’s Guide
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HAPTER
82
DHCP
82.1 DHCP Overview
DHCP (Dynamic Host Configuration Protocol RFC 2131 and RFC 2132) allows individual computers to
obtain TCP/IP configuration at start-up from a server. You can configure the OLT as a DHCP server or a
DHCP relay agent. When configured as a server, the OLT provides the TCP/IP configuration for the
clients. If you configure the OLT as a relay agent, then the OLT forwards DHCP requests to DHCP server
on your network. If you don’t configure the OLT as a DHCP server or relay agent then you must have a
DHCP server in the broadcast domain of the client computers or else the client computers must be
configured manually.
82.1.1 DHCP Modes
The OLT can be configured as a DHCP server or DHCP relay agent.
• If you configure the OLT as a DHCP server, it will maintain the pool of IP addresses along with subnet
masks, DNS server and default gateway information and distribute them to your LAN computers.
• If there is already a DHCP server on your network, then you can configure the OLT as a DHCP relay
agent. When the OLT receives a request from a computer on your network, it contacts the DHCP
server for the necessary IP information, and then relays the assigned information back to the
computer.
82.1.2 DHCP Configuration Options
The DHCP configuration on the OLT is divided into Global and VLAN . Which you should use for
configuration depends on the DHCP services you want to offer the DHCP clients on your network.
Choose the configuration based on the following criteria:
• Global - The OLT forwards all DHCP requests to the same DHCP server.
• VLAN - The OLT is configured on a VLAN by VLAN basis. The OLT can be configured as a DHCP server
for one VLAN and at the same time the OLT can be configured to relay DHCP requests for clients in
another VLAN.
82.2 DHCP Relay
Configure DHCP relay on the OLT if the DHCP clients and the DHCP server are not in the same broadcast
domain. During the initial IP address leasing, the OLT 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 OLT.