Chapter 8 Home Networking
EX5501-B0 / AX7501-B0 / PX7501-B0 User’s Guide
142
8.9.3 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.
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.
8.9.4 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.
IP Address and Subnet Mask
Similar to the way houses on a street share a common street name, so too do computers on a LAN share
one common network number.
Where you obtain your network number depends on your particular situation. If the ISP or your network
administrator assigns you a block of registered IP addresses, follow their instructions in selecting the IP
addresses and the subnet mask.
If the ISP did not explicitly give you an IP network number, then most likely you have a single user
account and the ISP will assign you a dynamic IP address when the connection is established. If this is
the case, it is recommended that you select a network number from 192.168.0.0 to 192.168.255.0 and
you must enable the Network Address Translation (NAT) feature of the Zyxel Device. The Internet
Assigned Number Authority (IANA) reserved this block of addresses specifically for private use; please do
not use any other number unless you are told otherwise. Let's say you select 192.168.1.0 as the network
number; which covers 254 individual addresses, from 192.168.1.1 to 192.168.1.254 (zero and 255 are
reserved). In other words, the first three numbers specify the network number while the last number
identifies an individual computer on that network.
Once you have decided on the network number, pick an IP address that is easy to remember, for
instance, 192.168.1.1, for your Zyxel Device, but make sure that no other device on your network is using
that IP address.
The subnet mask specifies the network number portion of an IP address. Your Zyxel Device will compute
the subnet mask automatically based on the IP address that you entered. You do not need to change
the subnet mask computed by the Zyxel Device unless you are instructed to do otherwise.
