ZyXEL Communications VMG1312-T10C, User Manual

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Chapter 7 Home Networking
VMG1312-T10C User’s Guide
102
LAN TCP/IP
The 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 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 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 Device will compute
the subnet mask automatically based on the IP address that you entered. You don't need to change
the subnet mask computed by the Device unless you are instructed to do otherwise.
Private IP Addresses
Every machine on the Internet must have a unique address. If your networks are isolated from the
Internet, for example, only between your two branch offices, you can assign any IP addresses to
the hosts without problems. However, the Internet Assigned Numbers Authority (IANA) has
reserved the following three blocks of IP addresses specifically for private networks:
• 10.0.0.0 — 10.255.255.255
• 172.16.0.0 — 172.31.255.255
• 192.168.0.0 — 192.168.255.255
You can obtain your IP address from the IANA, from an ISP or it can be assigned from a private
network. If you belong to a small organization and your Internet access is through an ISP, the ISP
can provide you with the Internet addresses for your local networks. On the other hand, if you are
part of a much larger organization, you should consult your network administrator for the
appropriate IP addresses.
Note: Regardless of your particular situation, do not create an arbitrary IP address;
always follow the guidelines above. For more information on address assignment,
please refer to RFC 1597, “Address Allocation for Private Internets” and RFC 1466,
“Guidelines for Management of IP Address Space”.