Basic Networking 101
Article ID = 57Article Title = Basic Networking 101
Article Author(s) = Graham Needham (BH)
Article Created On = 10th January 2012
Article Last Updated = 18th April 2018
Article URL = https://www.macstrategy.com/article.php?57
Article Brief Description:
Basic TCP/IP v4 networking configuration information
Basic Networking 101
This is a very rudimentary, quick guide to the basics of TCP/IP v4 networking.IP Addresses
You should think of IP addressing like telephone numbers. Telephone numbers consist of three parts:- Country code e.g. 44 (for the United Kingdom).
- Area code e.g. 0207 (for London).
- The number e.g. 123 4567.
- Country code = 192.
- Area code = 168.0.
- The number = 1
NOTE: The IP address and Subnet Mask actually break down to binary numbers but that's beyond the scope of this article.
The free to use (also known as "private") network ranges are:
- 10.0.0.0 - 10.255.255.255
- 172.16.0.0 - 172.31.255.255
- 192.168.0.0 - 192.168.255.255
- IP addresses 10.0.0.1 - 10.0.0.254 with a subnet mask of 255.255.255.0
- IP addresses 172.16.0.1 - 172.16.0.254 with a subnet mask of 255.255.255.0
- IP addresses 192.168.0.1 - 192.168.0.254 with a subnet mask of 255.255.255.0
- IP addresses 10.0.0.1 - 10.0.254.254 with a subnet mask of 255.255.0.0
- IP addresses 172.16.0.1 - 172.16.254.254 with a subnet mask of 255.255.0.0
- IP addresses 192.168.0.1 - 192.168.254.254 with a subnet mask of 255.255.0.0
Networks
A single network consists of at least two devices using the same area code (and thus same subnet mask) and with their own number.NOTE: Each device on the same network must have a unique number.
So in the above example computer one has the IP address 10.0.0.1 (with subnet mask 255.255.255.0)
and the second computer has the IP address 10.0.0.2 (with the same subnet mask). Voila, you've
created your own network.
Networks can be wired or wireless. To expand a single network hubs, switches and bridges are used.
- Hub = connects multiple Ethernet devices but is unsophisticated, has no control facilities and has limitations on large networks
- Switch = connects multiple Ethernet devices - range from small/basic e.g. 5/8 port to very large, fast, fibre channel linked and/or manageable versions
- Bridge = used to "bridge" two different types of physical network e.g. wired ethernet and wireless such as a wireless access point NOTE: With costs having dramatically lowered over the years switches are now almost always recommended over and above hubs.
To join two different networks together a router must be used to "route" traffic between
them. A router can connect two different networks using two different country/area codes using
Network Address Translation (NAT). If
you want to protect traffic going from one network
to another you use a firewall (often a router is also a firewall). Firewalls can be
programmed to allow or not allow certain types of data (protocols) in and/or out.
Modern routers can be very complex actually performing many different types of tasks including an
ethernet switch, NAT, firewall, DHCP server, bridge, etc. For a device on a network with a router to
be able to connect to a device on a different network the router's IP address needs to be added to
your device's network configuration.
DNS (Domain Name Server)
When you use the internet you don't generally type IP addresses in and it would also be silly as you'd have to remember lots of IP addresses to be able to visit web sites. So just like in the real world where you don't have to remember lots of telephone numbers you can look up a number in a directory e.g. the yellow pages for businesses. Computer networking uses the same principles. There are directories called "Domain Name Servers" (DNS for short). Just as there are multiple directories in the real world you can add more than one DNS server to your computer's network configuration. Your "local" DNS server is usually provided by your Internet Service Provider (ISP) but you can also use global ones such as:- Cloudflare (privacy-first consumer DNS service)
- OpenDNS
- FreeDNS
- Google DNS
- Go to Apple menu > System Preferences > Network
- For each required network port on the left:
- Select the network port on the left
- Click the "Advanced…" button the right
- Click the "DNS" tab
- Under 'DNS Servers' click the "+" button at the bottom
- If not already in the list, add the DNS servers "1.1.1.1" and "1.0.0.1"
- If necessary click and drag "1.1.1.1" and "1.0.0.1" to first and second in the list
Static/Dynamic IP Addressing
When you connect a device such as your computer, iPhone or iPad to a network for it to work on that network it must have a unique IP address. Instead of having to manually enter IP address settings individually on each and every device you can automate this process by using a DHCP server. If the device has the same IP address (such as one entered manually or specifically given to it by a DHCP server every time it is turned on) it is known as a "static" IP address. If the address is given out by a DHCP server from a "pool" of addresses and the address changes over time then it is a known as a "dynamic" IP address.DHCP server (Dynamic Host Control Protocol)
DHCP servers handle the automated process of giving out TCP/IP information to devices on a network. They are usually given a pool of addresses to use and other addresses in the network range are reserved for static use e.g.- Network range = 192.168.0.0 to 192.168.0.255
- Subnet mask = 255.255.255.0
- IP address range = 192.168.0.1 to 192.168.0.254
- DHCP "dynamic" IP address pool = 192.168.0.1 to 192.168.0.200
- Reserved "static" IP addresses = 192.168.0.201 to 192.168.0.254
NOTE: You must only have one DHCP server active on a single network at any given time.
NOTE: You must make sure that any static IP addresses used are not in the DHCP pool otherwise network conflicts may occur.
Real World Network Example
So for your computer or any other network device to operate properly on a given network it must have four bits of information:- IP Address
- Subnet Mask
- Router
- DNS Server(s) NOTE: On a Mac these are found at Apple menu > System Preferences > Network and then select your network connection type on the left.
In the above real world home or office network example there are multiple network devices connected to a broadband router which is connected to the internet. The router is handling ethernet switch, routing, NAT, DHCP server and firewall duties. There is also a wireless access point on the network in bridge mode but it is entirely possible for the router to also be acting as a wireless access point along with all the other duties.
- Network range = 10.0.0.0 to 10.0.0.255
- Subnet mask = 255.255.255.0
- IP address range = 10.0.0.1 to 10.0.0.254
- DHCP "dynamic" IP address pool = 10.0.0.1 to 10.0.0.200
- Reserved "static" IP addresses = 10.0.0.201 to 10.0.0.254
- Static IP address usage:
- Router IP address = 10.0.0.254
- Apple Airport Base Station for wireless clients (bridge mode) = 10.0.0.250
- Additional static network devices = 10.0.0.251 to 10.0.0.253
- Media server e.g. iTunes Server = 10.0.0.240
- Additional servers = 10.0.0.241 to 10.0.0.249
- Networked Printer = 10.0.0.230
- Additional networked printers = 10.0.0.231 to 10.0.0.239
- Networked media device e.g. Apple TV = 10.0.0.220
- Additional networked media devices e.g. Playstation, Xbox, Wii, TV, blu-ray player = 10.0.0.221 to 10.0.0.229
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