User's Manual

Appendix C IP Addresses and Subnetting
NWA1121-NI User’s Guide
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Configuring IP Addresses
Where you obtain your network num ber depends on your particular situat ion. If the ISP or your
network adm inistrator assigns you a block of registered I P addresses, follow their instructions in
selecting the I P addresses and the subnet mask.
If the I SP did not explicitly give you an I P network number, then most likely you have a single user
account and the I SP will assign you a dynam ic IP address when the connection is established. If this
is the case, it is recom m ended that you select a network num ber from 192.168.0.0 to
192.168.255.0. The I nternet Assigned Number Authority ( I ANA) reserved this block of addresses
specifically for private use; please do not use any other number unless you are told otherwise. You
must also enable Network Address Translation (NAT) on the NWA1121-NI .
Once you have decided on the network num ber, pick an IP address for your NWA1121-NI that is
easy to remem ber (for instance, 192.168.1.1) but make sure that no other device on your network
is using that IP address.
The subnet mask specifies the network num ber portion of an I P address. Your NWA1121-NI will
compute the subnet mask autom atically based on the IP address that you entered. You don't need
to change the subnet mask com puted by the NWA1121-NI unless you are instructed to do
otherwise.
Private IP Addresses
Every m achine on the Internet must have a unique address. I f your networks are isolated from the
Internet (running only between two branch offices, for exam ple) you can assign any I P addresses to
the hosts without problems. However, the I nternet Assigned Numbers Authority (I ANA) 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 I SP, or it can be assigned from a private
network. I f you belong to a small organization and your I nternet access is through an I SP, the I SP
can provide you with the I nternet 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.
Regardless of your particular situation, do not create an arbitrary I P address; always follow the
guidelines above. For m ore information on address assignm ent, please refer to RFC 1597, Address
Allocat ion for Privat e I nternets and RFC 1466, Guidelines for Managem ent of I P Address Space.
13 255.255.255.248 (/ 29) 8192 6
14 255.255.255.252 (/ 30) 16384 2
15 255.255.255.254 (/ 31) 32768 1
Table 52 16-bit Network Number Subnet Planning (continued)
NO. “BORROWED”
HOST BITS
SUBNET MASK NO. SUBNETS
NO. HOSTS PER
SUBNET