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(Last modified: Friday, September 9, 2016 11:58 am)

What IP Address Should I Use for Network Devices?

How can I access a local device from outside the local network?

What IP Address Should I Use for Network Devices?

Internet Protocol (IP) addresses are in the form ###.###.###.### where ### is a decimal
number in the range 0-255.

Private networks are designated three address ranges (subnet mask):
10.0.0.0 - 10.255.255.255 (255.0.0.0)
172.16.0.0 - 172.31.255.255 (255.240.0.0)
192.168.0.0 - 192.168.255.255 (255.255.0.0)

Since most homes have fewer than 256 internet connected devices, it is common to use
192.168.10.### (255.255.255.0) for inside IP addresses.
In this case, 10 is a number unique among all the networks we need to connect to via
Virtual Private Network (VPN). If you do not need to connect to other networks with VPN,
use 192.168.1.### as this is a common default range for devices.
Many choose to make the Router IP a high number that is outside the DHCP range, like:
192.168.10.254

Dynamic Host Configuration Protocol (DHCP) is a function the router performs to automatically
pass out IP addresses to devices on the network. This address is subject to change each time
the device connects to the network. So, if you have a device like a camera that you want to
bookmark and be sure it will always have the same IP address, set up the device with a static
IP address and configure the Router DHCP Starting IP Address to reserve a number of
addresses at the beginning of your range, like 50. That will reserve the first 50 IP addresses
in your range for static IP devices. The Maximum Number of DHCP Users: 50 setting
designates that only 50 IP addresses will be issued allowing you to use high IP addresses (like
192.168.10.254) for Routers, Switches, and Wireless Access Points (WAP).

While you can use any addresses outside the DHCP range you wish for static IP addresses,
this approach simplifies things in this way. You can assume your Routers, Switches, and WAPs
are addressed 192.168.10.254, 192.168.10.253, 192.168.10.252 ..., and you can assume your devices
on the network are addressed 192.168.10.1, 192.168.10.2, 192.168.10.3 ... Nevertheless, writing
down the static IP addresses you assign to your devices will save you a lot of time and
frustration when you need to access them.


How can I access a local device from outside the local network?

All internet connected devices must have a unique IP address. This address is a number represented
by 4 decimal numbers separated by a "dot" (or period). Like ###.###.###.###. Each of the 4 numbers
is in the range 0-255.

We can access addresses by names indirectly through the Domain Name System (DNS). This is a
service provided by a large number of servers that returns the IP address associated with a name.

If you want to access servers or devices on your local network by name, you must have a local server
that provides DNS service for your local network. If you don't have a server that can provide DNS,
you can edit the hosts file (%windir%System32\drivers\etc\hosts) on each workstation.

Dynamic Host Configuration Protocol (DHCP) is an internet service that provides IP addresses to
devices to avoid conflicting addresses. Servers and devices that need to be accessed by workstations
need to have the same IP address and are normally assigned a static IP address. The DHCP server you
use, which is typically on your local router, needs to be configured to exclude a range of addresses
used as static addresses. Most Internet Service Providers (ISP) use DHCP to dynamically assign an
IP address for your local network and charge an extra monthly fee for each static address. Internet
services like noip may be used to access a your local network
even if the address changes using Dynamic DNS (DDNS or DynDNS), a method of automatically updating
a name server in the Domain Name System in real time. Most ISP's change your local network IP address
very infrequently.

To determine your local network's IP address, use whatsmyip.net or just type
whatsmyip in Google. Once you have your outside IP
address, you can access your local network from anywhere on the internet. The address is the address
of your router, which may be a computer, or a router device with limited functionality. If you have a
server and the server is running web server software (like Apache or Microsoft Internet Information Server
(IIS)), the outside address will return the home page of the web server. If you have a router device,
the address will connect to the device.

To access another device (that is not your router) on your local network, like a camera, you can use
port forwarding. A IP port number is used along with the IP address to determine where to route network
traffic. There are certain ports reserved as the default port for specific uses. Hypertext Transfer
Protocol (HTTP) for example uses port 80 by default for web server traffic, HTTPS port 443, File Transfer
Protocol (FTP) port 20, Internet Message Access Protocol (IMAP) port 143,
(see Wikipedia: List of TCP and UDP port numbers for many others.
In a browser, a port may be designated by ###.###.###.###:ppp where ppp is the port number. For example,
https://www.google.com:443 may be used to access Google. The :443 is
not necessary only because 443 is the default port for https.

Most router devices may be configured to do port forwarding. In the router configuration, this feature
may be called Applications & Gaming. Select a unique port (not a reserved as
a default port) and map the port to a local IP address. When you add this port number to the end of the
outside address of your router, the router forwards the traffic to the associated local IP address. The
device itself may need to be configured to use the same port number.