ZyXEL Communications MAX-306M1, User Manual

Page: 82 / 376

Chapter 7 The LAN Configuration Screens
User’s Guide
82
7.6.4 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 in DHCP Setup, 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 WiMAX Modem supports the IPCP DNS server extensions through
the DNS proxy feature.
If the Primary and Secondary DNS Server fields in the LAN Setup screen are
not specified, for instance, left as 0.0.0.0, the WiMAX Modem tells the DHCP
clients that it itself is the DNS server. When a computer sends a DNS query to the
WiMAX Modem, the WiMAX Modem 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 LAN Setup screen. This way, the
WiMAX Modem can pass the DNS servers to the computers and the computers can
query the DNS server directly without the WiMAX Modem’s intervention.
7.6.5 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:
• Both - the WiMAX Modem will broadcast its routing table periodically and
incorporate the RIP information that it receives.
• In Only - the WiMAX Modem will not send any RIP packets but will accept all
RIP packets received.
• Out Only - the WiMAX Modem will send out RIP packets but will not accept any
RIP packets received.