ZyXEL Communications MAX218M2W User Manual page 92

Chapter 7 Network Setting
DNS Server Address
DNS (Domain Name System) is for mapping 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 machine before you can access it.
The DNS server addresses that you enter in the DHCP setup 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 first
is for an ISP to tell a customer the DNS server addresses, usually in the form of an
information sheet, when s/he signs up. If your ISP gives you the DNS server
addresses, enter them in the DNS Server fields; otherwise, leave them blank.
Some ISPs choose to pass the DNS servers using the DNS server extensions of
PPP 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 MAX208M2W Series supports the IPCP DNS server extensions
through the DNS proxy feature.
If the Primary and Secondary DNS Server fields are not specified, for instance,
left as 0.0.0.0, the MAX208M2W Series tells the DHCP clients that it itself is the
DNS server. When a computer sends a DNS query to the MAX208M2W Series, the
MAX208M2W Series 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. This way, the MAX208M2W Series can pass
the DNS servers to the computers and the computers can query the DNS server
directly without the MAX208M2W Series's intervention.
RIP Setup
RIP (Routing Information Protocol) allows a router to exchange routing
information with other routers. The RIP Direction field controls the sending and
receiving of RIP packets. When set to:
• RX/TX - the MAX208M2W Series will broadcast its routing table periodically and
incorporate the RIP information that it receives.
• RX Only - the MAX208M2W Series will not send any RIP packets but will accept
all RIP packets received.
• TX Only - the MAX208M2W Series will send out RIP packets but will not accept
any RIP packets received.
• None - the MAX208M2W Series will not send any RIP packets and will ignore
any RIP packets received.
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MAX208M2W Series User's Guide