ifconfig
============
Your connection to a network is made by your system through a
particular hardware interface such as an Ethernet card of a modem. Data passing
through this interface is then routed to your network. The ifconfig command
configures your network interfaces and the route command sets up the network
connections accordingly.
Ifconfig is used to configure the kernel-resident network
interfaces.It is used at boot time to set up interfaces as necessary. If no
arguments are given, ifconfig displays the status of the currently active
interfaces. If a single interface argument is given, it displays the status of
the given interface only.
Syntax : ifconfig < interface > <
-host_net_flag > [address] [options]
where -host_net_flag can
be either -host or -net to indicate a host or network IP address.
The -host flag
is the default.
Usage
Examples
#ifconfig eth0
192.168.0.1 =>
Configuring the Ethernet interface
#ifconfig eth0
192.168.0.1 broadcast
192.168.0.255 netmast 255.255.255.0 => Configuring eth0 including a
broadcast address and the netmask
#ifconfig eth0 up => To activate the interface eth0
after configuring it
#ifconfig -a
=> If a single -a
argument is given, it displays the status of all interfaces, even those that
are down
Route
===========
Determines where the process starts and to what computer your
system needs to send the packet to reach the destination.
Usage
Examples
#route => To display the routing table
#route add 192.168.1.2
dev eth0 => To
route an Ethernet interface
#route del 192.168.1.2 => To delete the route with IP
address 192.168.1.2
For a gateway we first need to add a route and then add a route
specifying it is a gateway.
#route add 192.168.1.2
#route add default gw
192.168.1.2 => gw
here stands for gateway
#route add -net
192.168.23.0 gw dev eth1 =>
For a gateway to access a subnet
To add an IP address to another network interface we use the
ifcofig and route commands with the new IP address.
#ifcofig eth1
192.168.1.3
#route add 192.168.1.3
dev eth1
ARP
===========
ARP stands for Address Resolution Protocol, which is used to
find the media access control address of a network neighbour for a given IPv4
Address.
Usage
Examples
#arp -e => Display all ARP table entries for
all interfaces
#arp -i eth0 -s
192.168.1.1 00:23:5a:c1:50:99 => Create a static ARP table entry associating IP
address 192.168.1.1 with MAC address 00:23:5a:c1:50:99 available through the
eth0 interface ( ‘i’ option stands for interface and ‘s’ option is used for
setting up new table entry )
#arp -d 192.168.1.1 => Delete the ARP table entry for
192.168.1.1
Traceroute
===================
Traceroute is a utility that traces a packet from your computer
to an Internet host showing how many hops the packet requires to reach the host
and how long each hop takes.For a slow connection traceroute is used to check
the route through which we are connected to a host , monitoring the speed and
the number of intervening gateway connections a route takes.
Usage
Example
#traceroute
www.google.com
Sample Output for the
above command:
traceroute to www.google.com (74.125.236.48), 30 hops max, 60
byte packets
1 172.19.16.1 (172.19.16.1) 1694.355 ms 1694.510 ms 1694.847 ms
2 iws1.iiita.ac.in (172.31.1.1) 0.869 ms 0.864 ms 0.902 ms
3 * * *
4 * * *
5 115.114.57.161.static-Mumbai.vsnl.net.in (115.114.57.161)
66.756 ms 66.750 ms 66.730 ms
6 115.113.163.70.static-pune.vsnl.net.in (115.113.163.70) 69.556
ms 69.287 ms 69.279 ms
7 209.85.241.52 (209.85.241.52) 62.766 ms 62.797 ms 64.210 ms
8 209.85.251.95 (209.85.251.95) 64.153 ms 64.162 ms 65.593 ms
9 209.85.241.33 (209.85.241.33) 65.855 ms 65.849 ms 64.820 ms
10 maa03s04-in-f16.1e100.net (74.125.236.48) 62.011 ms 62.001 ms
61.982 ms
netstat
================
Provides real time information on the status of the network
connections, as well as the network statistics and routing table.
Usage
Examples
#netstat -r =>
Displays the routing table
#netstat -i
=> Displays the uses of the different network interfaces.
#netstat -s => Displays
protocol( TCP , UDP , IP etc ) counts and errors
telnet
============
To remotely log in to another system on your network. Telnet
operates as if we were logging in to another system from a remote terminal and
asks for the login name and password.
#telnet hostname <
port >
or
#telnet
telnet > open
hostname < port >
Here the hostname can be either the domain name or the IP
address.
Nslookup
=====================
Nslookup is a command used to query the Internet domain name
servers. Is useful in finding the domain name if the IP is known and
vice-versa.
The host command can be used to carry out the same stuff too.
Usage
Examples
#nslookup < domain
name > => To find the dotted decimal IP
address of host name
#nslookup < IP
address > => To find the
hostname of the dotted decimal IP address
Ping
==========
Detects whether a system is up and running.
Syntax : ping hostname
where hostname can be
either domain name or IP address.
Usage
Examples
#ping 172.19.16.47
From 172.19.16.47 icmp_seq=1 Destination Host Unreachable
From 172.19.16.47 icmp_seq=2 Destination Host Unreachable
From 172.19.16.47 icmp_seq=3 Destination Host Unreachable
From 172.19.16.47 icmp_seq=4 Destination Host Unreachable
From 172.19.16.47 icmp_seq=5 Destination Host Unreachable
From 172.19.16.47 icmp_seq=6 Destination Host Unreachable
#ping 172.19.16.6
PING 172.19.16.6 (172.19.16.6) 56(84) bytes of data.
64 bytes from 172.19.16.6: icmp_req=1 ttl=128 time=4.00 ms
64 bytes from 172.19.16.6: icmp_req=2 ttl=128 time=4.56 ms
64 bytes from 172.19.16.6: icmp_req=3 ttl=128 time=0.931 ms
64 bytes from 172.19.16.6: icmp_req=4 ttl=128 time=4.10 ms
64 bytes from 172.19.16.6: icmp_req=5 ttl=128 time=1.08 ms
64 bytes from 172.19.16.6: icmp_req=6 ttl=128 time=6.78 ms
Here in the first case the destination host is unreachable
whereas in the second case the destination 172.19.6.16 sends the packets back
ensuring good connectivity.
ssh
========
ssh (SSH client) is a program for logging into a remote machine
and for executing commands on a remote machine. It is intended to replace
rlogin and rsh, and provide secure encrypted communications between two
untrusted hosts over an insecure network.
Syntax : ssh username@hostname
[command]
where username is your SSH username, and hostname is the host
name or IP address of your Web server.
If its the first time we are trying to connect to this host
machine we will get a warning saying authentication failure. Typing yes would
automatically solve the problem.
Usage
Examples
#ssh raju@192.168.1.1
-p 1020 => ssh as
user raju into 192.168.1.1 port 1020
#ssh raju@192.168.1.1
cd /home/etc => change the
directory to /home/etc in the remote server 192.168.1.1
Read More : http://www.fortystones.com/40-basic-linux-command-line-tips-tricks/
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