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8.9.4 LAN TCP/IP
The EMG 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 EMG. 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 EMG, 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 EMG 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 EMG 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
• 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".
Chapter 8 Home Networking
— 10.255.255.255
EMG6726/8726-B10A User's Guide
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