Linux Commands Network Configuration and Troubleshooting

Computers are connected in a network to exchange information or resources each other. Two or more computer connected through network media called computer network. There are number of network devices or media are involved to form computer network. Computer loaded with Linux Operating System can also be a part of network whether it is small or large network by its multitasking and multiuser natures. Maintaining of system and network up and running is a task of System / Network Administrator’s job. In this article we are going to review frequently used network configuration and troubleshoot commands in Linux.


ifconfig (interface configurator) command is use to initialize an interface, assign IP Address to interface and enable or disable interface on demand. With this command you can view IP Address and Hardware / MAC address assign to interface and also MTU (Maximum transmission unit) size.

# ifconfig 


ifconfig with interface (eth0) command only shows specific interface details like IP Address, MAC Address etc. with -a options will display all available interface details if it is disable also.

# ifconfig eth0


Assigning IP Address and Gateway

Assigning an IP Address and Gateway to interface on the fly. The setting will be removed in case of system reboot.

# ifconfig eth0 netmask

Enable or Disable Specific Interface

To enable or disable specific Interface, we use example command as follows.

Enable eth0

# ifup eth0

Disable eth0

# ifdown eth0


Setting MTU Size

By default MTU size is 1500. We can set required MTU size with below command. Replace XXXX with size.

# ifconfig eth0 mtu XXXX


Set Interface in Promiscuous mode

Network interface only received packets belongs to that particular NIC. If you put interface in promiscuousmode it will received all the packets. This is very useful to capture packets and analyze later. For this you may require superuser access.

# ifconfig eth0 -promise


2-PING Command

PING (Packet INternet Groper) command is the best way to test connectivity between two nodes. Whether it is Local Area Network (LAN) or Wide Area Network (WAN). Ping use ICMP (Internet Control Message Protocol) to communicate to other devices. You can ping host name of ip address using below command.

# ping

# ping

In Linux ping command keep executing until you interrupt. Ping with -c option exit after N number of request (success or error respond).

# ping -c 5



traceroute is a network troubleshooting utility which shows number of hops taken to reach destination also determine packets traveling path. Below we are tracing route to global DNS server IP Address and able to reach destination also shows path of that packet is traveling.

# traceroute


4-NETSTAT Command

Netstat (Network Statistic) command display connection info, routing table information etc. To displays routing table information use option as -r.

# netstat -r

Kernel IP routing table

Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface    *        U         0 0          0 eth0

link-local      *          U         0 0          0 eth0

default         UG        0 0          0 eth0


5-DIG Command

Dig (domain information groper) query DNS related information like A Record, CNAME, MX Record etc. This command mainly use to troubleshoot DNS related query.

# dig; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.10.rc1.el6 <<>>


6-NSLOOKUP Command

nslookup command also use to find out DNS related query. The following examples shows A Record (IP Address) of

# nslookup



Non-authoritative answer: canonical name =





7-ROUTE Command

route command also shows and manipulate ip routing table. To see default routing table in Linux, type the following command.

# route

Kernel IP routing table

Destination     Gateway         Genmask         Flags Metric Ref    Use Iface    *        U     0      0        0 eth0

link-local      *          U     1002   0        0 eth0

default         UG    0      0        0 eth0

Adding, deleting routes and default Gateway with following commands.

Route Adding

# route add -net gw

Route Deleting

# route del -net gw

Adding default Gateway

# route add default gw


8-HOST Command

host command to find name to IP or IP to name in IPv4 or IPv6 and also query DNS records.

# host has address has address has address has address has address has IPv6 address 2404:6800:4003:802::1014

Using -t option we can find out DNS Resource Records like CNAME, NS, MX, SOA etc.

# host -t CNAME is an alias for


9-ARP Command

ARP (Address Resolution Protocol) is useful to view / add the contents of the kernel’s ARP tables. To see default table use the command as.

# arp -e

Address                  HWtype  HWaddress           Flags Mask            Iface             ether   00:50:56:c0:00:08   C                     eth0


10-ETHTOOL Command

ethtool is a replacement of mii-tool. It is to view, setting speed and duplex of your Network Interface Card (NIC). You can set duplex permanently in /etc/sysconfig/network-scripts/ifcfg-eth0 with ETHTOOL_OPTS variable.

# ethtool eth0

Settings for eth0:

Current message level: 0x00000007 (7)

Link detected: yes


11-IWCONFIG Command

iwconfig command in Linux is use to configure a wireless network interface. You can see and set the basic Wi-Fi details like SSID channel and encryption. You can refer man page of iwconfig to know more.

# iwconfig [interface]


12-HOSTNAME Command

hostname is to identify in a network. Execute hostname command to see the hostname of your box. You can set hostname permanently in /etc/sysconfig/network. Need to reboot box once set a proper hostname.

# hostname

13-GUI tool system-config-network

Type system-config-network in command prompt to configure network setting and you will get nice Graphical User Interface (GUI) which may also use to configure IP Address, Gateway, DNS etc. as shown below image.

# system-config-network