Computer on the network
Network is a collection of two or more hosts (computers) that communicates with each
other. Communication can be via a wired connection or wireless. Internet is an example of
a network. It connects millions of computers throughout a publically accessible network. Many people use
the Internet to surf web pages and send or receive e-mail, but the Internet has many additional
capabilities besides these. Router is a device that connects computers from one network to
another. For example, if you are in office, the computers within the company can all communicate via the
local network. To access the Internet, the computers would have to communicate with a router that would be
used to forward network communications to the Internet. An IP (Internet Protocol) address is a unique
number assigned to a host (computer) on a network. Hosts use these numbers for network communication
between them. There are two different types of IP addresses: IPv4 and
IPv6. IPv4 (IP version 4) was used by all computers for many years. In IPv4 address, a
total of four 8-bit (8-bit = numbers from 0 to 255) numbers are used to define the address. For example,
this is considered a 32-bit address (4 x 8-bit = 32):
192.168.1.1. Each host on the Internet
must have a unique IP address. In an IPv4 environment, there is a technical limit of IP addresses. However,
many of these IP addresses have been assigned to organizations. While it seems like there should be plenty
of IP addresses, the Internet started running out of IP addresses. This problem encouraged the development
of IPv6 (IP version 6). In IPv6 network the addresses are much larger, 128-bit addresses that look like
2001:0db8:85a3:0042:1000:8a2e:0370:7334. The difference between IPv4 and IPv6 isn't just
more IP addresses. IPv6 has many other advanced features that address some of IPv4's limitations. The
majority of network devices in the world still use IPv4. Most experts agree that IPv6 will eventually
When a computer is asked to access a website, such as
www.example.com, it does not necessarily
know what IP address to use. In order for the computer to associate an IP address with the URL or hostname
request, the computer relies upon the DNS. The address of the DNS server is stored in the
/etc/resolv.conf file. This file is automatically generated. The nameserver is often set to
the IP address of the DNS server.
$ cat /etc/resolv.conf
It is common to have multiple nameserver if one DNS server isn't responding.
contains a table of hostnames to IP addresses. It can be used to supplement a DNS server.
$ cat /etc/hosts
ifconfig stands for "interface configuration" and is used to display network configuration
ifconfig is being replaced with a
ip addr show in some Linux
distributions. Router (or gateway) is a device that will allow hosts from one network to communicate with
another network. To view a table that describes where network packages are sent, use
0.0.0.0 refers to "all other machines".
route is being
ip route show in some Linux distributions.
ping can be used to
determine if another host is reachable. If
ping can send a network package to another host and
receive a response, then you should be able to connect to that host. By default, the
continue sending packages. To limit how many pings to send, use the
$ ping -c 5 google.com
Some administrators configure their hosts to not respond to ping requests. This is because a server can be attacked and overwhelmed by a massive number of network packets. By ignoring ping requests, the server is less vulnerable.
ping may be useful for checking the availability of local hosts. The
netstat is a powerful tool that provides a large amount of network information. For example,
-i option to display statistics regarding network traffic. Use the
if you want to display routing information. The
netstat is also used to display open ports. A
port is a unique number that is associated with a service provided by a host. If the port is open, then the
service is available for other hosts. To see a list of all currently open ports, you can use
-t stands for TCP (protocol) and
-l stands for
"listening" (which ports are listening). If you want to show numbers, not names, add
option. On some distributions
netstat is obsolete. While no further development is being done
netstat, it is still an excellent tool for displaying network information and widely
used. The goal is to eventually replace
However, this may take some time.
host works with DNS to associate a hostname with an IP
$ host ajkule.org
host can be used if an IP address is known, but the domain name is not.
$ host 220.127.116.11
Other options exist to query the various aspects of a DNS such as
-t SOA or a comprehensive list of DNS information using the
-a (all) option.
If you have a desktop environment, you will also have access to a tool that will allow you to configure your network. If your network doesn't automatically assign network settings to your computer, you may have to manually enter the settings yourself. The following examples were performed in Debian desktop environment. To manually set your network settings, open the "Activities" overview and start typing "Settings", then click on "Settings".
If you are connected to the network with a cable, click "Network". Otherwise click "Wi-Fi", then click the settings icon next to the active network.
You can see connection details
or select the IPv4 or IPv6 tab and change the "Method" to "Manual".