Chapter 8 Home Networking
VMG1312-B Series User’s Guide
159
• Som e I SPs choose to dissem inate the DNS server addresses using the DNS server extensions of
I PCP ( I P Control Prot ocol) aft er the connection is up. I f your I SP did not give you explicit DNS
servers, chances are the DNS servers are conveyed t hrough I PCP negotiat ion. The Device
supports t he I PCP DNS server extensions t hrough t he DNS proxy feat ure.
Please not e t hat DNS proxy works only when the I SP uses the I PCP DNS server ext ensions. I t
does not m ean you can leave t he DNS servers out of t he DHCP setup under all circum stances. I f
your I SP gives you explicit DNS ser vers, m ake sure t hat you ent er t heir I P addresses in the
DH CP Set up screen.
8.10.4 LAN TCP/IP
The Device has built- in DHCP server capabilit y t hat assigns I P addresses and DNS servers t o
system s t hat support DHCP client capabilit y.
IP Address and Subnet Mask
Sim ilar t o the way houses on a street share a com m on street nam e, so t oo do com puters on a LAN
share one com m on net work num ber.
Where you obtain your network num ber depends on your particular sit uation. I f the I SP or your
net work adm inistrator assigns you a block of registered I P addresses, follow t heir inst ruct ions in
selecting the I P addresses and the subnet m ask.
I f t he I SP did not explicitly give you an I P net work num ber, then m ost likely you have a single user
account and t he I SP will assign you a dynam ic I P address when t he connection is established. I f t his
is the case, it is recom m ended that you select a network num ber from 192.168.0.0 t o
192.168.255.0 and you m ust enable t he Net work Address Translation ( NAT) feat ure of the Device.
The I nt ernet Assigned Num ber Authority ( I ANA) reserved t his block of addresses specifically for
private use; please do not use any ot her num ber unless you are t old ot herw ise. Let 's say you select
192.168.1.0 as t he net work num ber; which covers 254 individual addresses, from 192.168.1.1 to
192.168.1.254 ( zero and 255 are reser ved). I n other words, the first t hree num bers specify t he
net work num ber while t he last num ber ident ifies an individual com puter on t hat net work.
Once you have decided on the network num ber, pick an I P address that is easy t o rem em ber, for
inst ance, 192.168.1.1, for your Device, but m ake sure t hat no other device on your netw ork is
using that I P address.
The subnet m ask specifies the network num ber port ion of an I P address. Your Device will com pute
the subnet m ask aut om atically based on t he I P address t hat you entered. You don't need to change
the subnet m ask com puted by t he Device unless you are inst ruct ed t o do ot herwise.
Private IP Addresses
Every m achine on t he I nt ernet m ust have a unique address. I f your networ ks are isolat ed from t he
I nternet, for exam ple, only between your two branch offices, you can assign any I P addresses to
the host s wit hout problem s. However, the I nt ernet Assigned Numbers Aut hority (I ANA) has
reserved the following three blocks of I P addresses specifically for private net works:
• 10.0.0.0 — 10.255.255.255
• 172.16.0.0 — 172.31.255.255
• 192.168.0.0 — 192.168.255.255
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