ZyXEL Communications P-2802H-I Series, User Manual

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Chapter 7 LAN Setup
P-2802H(W)(L)-I Series User’s Guide
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7.1.2 DHCP Setup
DHCP (Dynamic Host Configuration Protocol, RFC 2131 and RFC 2132) allows individual
clients to obtain TCP/IP configuration at start-up from a server. You can configure the ZyXEL
Device as a DHCP server or disable it. When configured as a server, the ZyXEL Device
provides the TCP/IP configuration for the clients. If you turn DHCP service off, you must
have another DHCP server on your LAN, or else the computer must be manually configured.
7.1.2.1 IP Pool Setup
The ZyXEL Device is pre-configured with a pool of IP addresses for the DHCP clients (DHCP
Pool). See the product specifications in the appendices. Do not assign static IP addresses from
the DHCP pool to your LAN computers.
7.2 DNS Server Addresses
DNS (Domain Name System) maps a domain name to its corresponding IP address and vice
versa. The DNS server is extremely important because without it, you must know the IP
address of a computer before you can access it. The DNS server addresses you enter when you
set up DHCP are passed to the client machines along with the assigned IP address and subnet
mask.
There are two ways that an ISP disseminates the DNS server addresses.
• The ISP tells you the DNS server addresses, usually in the form of an information sheet,
when you sign up. If your ISP gives you DNS server addresses, enter them in the DNS
Server fields in the DHCP Setup screen.
• Some ISPs choose to disseminate the DNS server addresses using the DNS server
extensions of IPCP (IP Control Protocol) after the connection is up. If your ISP did not
give you explicit DNS servers, chances are the DNS servers are conveyed through IPCP
negotiation. The ZyXEL Device supports the IPCP DNS server extensions through the
DNS proxy feature.
If the
DNS Server fields in the DHCP Setup screen are set to DNS Relay , the ZyXEL
Device tells the DHCP clients that it itself is the DNS server. When a computer sends a
DNS query to the ZyXEL Device, the ZyXEL Device acts as a DNS proxy and forwards
the query to the real DNS server learned through IPCP and relays the response back to the
computer.
Please note that DNS proxy works only when the ISP uses the IPCP DNS server
extensions. It does not mean you can leave the DNS servers out of the DHCP setup under
all circumstances. If your ISP gives you explicit DNS servers, make sure that you enter
their IP addresses in the
DHCP Setup screen.
7.3 LAN TCP/IP
The ZyXEL Device has built-in DHCP server capability that assigns IP addresses and DNS
servers to systems that support DHCP client capability.