13 Linux Network Configuration and Troubleshooting Commands
Computers are connected in a network to exchange information or resources with each other. Two or more computers are connected through network media called acomputer network. There is a number of network devices or media are involved to form a computer network.
Computer loaded withLinux Operating System can also be a part of network whether it is a small or large network by itsmultitasking and multiuser natures. Maintaining the system and network up and running is a task of theSystem / Network Administrator’s job.
[ You might also like:22 Linux Networking Commands for Sysadmin ]
In this article, we are going to review frequently used network configuration and troubleshoot commands in Linux.
1. ifconfig Command
ifconfig (interface configurator) command is used to initialize an interface, assignIP Address to interface andenable ordisable interface on demand.
With this command, you can viewIP Address andHardware /MAC address assign to interface and alsoMTU (Maximum transmission unit) size.
# ifconfigeth0 Link encap:EthernetHWaddr 00:0C:29:28:FD:4Cinet addr:192.168.50.2 Bcast:192.168.50.255 Mask:255.255.255.0 inet6 addr: fe80::20c:29ff:fe28:fd4c/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:6093 errors:0 dropped:0 overruns:0 frame:0 TX packets:4824 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:6125302 (5.8 MiB) TX bytes:536966 (524.3 KiB) Interrupt:18 Base address:0x2000lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:8 errors:0 dropped:0 overruns:0 frame:0 TX packets:8 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:480 (480.0 b) TX bytes:480 (480.0 b)
ifconfig with interface (eth0) command only shows specific interface details likeIP Address,MAC Address, etc. with-a option will display all available interface details if it is disabled also.
# ifconfig eth0eth0 Link encap:Ethernet HWaddr 00:0C:29:28:FD:4C inet addr:192.168.50.2 Bcast:192.168.50.255 Mask:255.255.255.0 inet6 addr: fe80::20c:29ff:fe28:fd4c/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:6119 errors:0 dropped:0 overruns:0 frame:0 TX packets:4841 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:6127464 (5.8 MiB) TX bytes:539648 (527.0 KiB) Interrupt:18 Base address:0x2000
Set IP Address and Gateway in Linux
Assigning anIP Address andGateway to the interface on the fly. The setting will be removed in case of a system reboot.
# ifconfig eth0 192.168.50.5 netmask 255.255.255.0
Enable or Disable Specific Interface
Toenable ordisable a specific Interface, we use the example command as follows.
Enable eth0
# ifup eth0
Disable eth0
# ifdown eth0
Setting MTU Size
By defaultMTU size is1500. We can set the requiredMTU size with the below command. ReplaceXXXX with size.
# ifconfig eth0 mtu XXXX
Set Interface in Promiscuous Mode
The network interface only received packets belonging to that particularNIC. If you put the interface in thepromiscuous mode it will receive all the packets. This is very useful to capture packets and analyze them later. For this, you may require superuser access.
# ifconfig eth0 - promisc
Update: Theifconfig command is replaced by theIP command in most modern Linux distributions.
2. Ping Command
Ping (Packet INternet Groper) command is the best way to test connectivity betweentwo nodes. Whether it isLocal Area Network (LAN) orWide Area Network (WAN).
Ping usesICMP (Internet Control Message Protocol) to communicate to other devices. You can ping hostname orip address using the below commands.
# ping 4.2.2.2PING 4.2.2.2 (4.2.2.2) 56(84) bytes of data.64 bytes from 4.2.2.2: icmp_seq=1 ttl=44 time=203 ms64 bytes from 4.2.2.2: icmp_seq=2 ttl=44 time=201 ms64 bytes from 4.2.2.2: icmp_seq=3 ttl=44 time=201 msOR# ping www.tecmint.comPING tecmint.com (50.116.66.136) 56(84) bytes of data.64 bytes from 50.116.66.136: icmp_seq=1 ttl=47 time=284 ms64 bytes from 50.116.66.136: icmp_seq=2 ttl=47 time=287 ms64 bytes from 50.116.66.136: icmp_seq=3 ttl=47 time=285 ms
In theLinux ping command keep executing until you interrupt. Ping with-c option exit afterN number of requests (success or error respond).
# ping -c 5 www.tecmint.comPING tecmint.com (50.116.66.136) 56(84) bytes of data.64 bytes from 50.116.66.136: icmp_seq=1 ttl=47 time=285 ms64 bytes from 50.116.66.136: icmp_seq=2 ttl=47 time=285 ms64 bytes from 50.116.66.136: icmp_seq=3 ttl=47 time=285 ms64 bytes from 50.116.66.136: icmp_seq=4 ttl=47 time=285 ms64 bytes from 50.116.66.136: icmp_seq=5 ttl=47 time=285 ms--- tecmint.com ping statistics ---5 packets transmitted, 5 received, 0% packet loss, time 4295msrtt min/avg/max/mdev = 285.062/285.324/285.406/0.599 ms
3. Traceroute Command
traceroute is a network troubleshooting utility that shows the number of hops taken to reach a destination also determines packets traveling path. Below we are tracing the route to the globalDNS server IP Address and able to reach destination also shows the path of that packet is traveling.
# traceroute 4.2.2.2traceroute to 4.2.2.2 (4.2.2.2), 30 hops max, 60 byte packets 1 192.168.50.1 (192.168.50.1) 0.217 ms 0.624 ms 0.133 ms 2 227.18.106.27.mysipl.com (27.106.18.227) 2.343 ms 1.910 ms 1.799 ms 3 221-231-119-111.mysipl.com (111.119.231.221) 4.334 ms 4.001 ms 5.619 ms 4 10.0.0.5 (10.0.0.5) 5.386 ms 6.490 ms 6.224 ms 5 gi0-0-0.dgw1.bom2.pacific.net.in (203.123.129.25) 7.798 ms 7.614 ms 7.378 ms 6 115.113.165.49.static-mumbai.vsnl.net.in (115.113.165.49) 10.852 ms 5.389 ms 4.322 ms 7 ix-0-100.tcore1.MLV-Mumbai.as6453.net (180.87.38.5) 5.836 ms 5.590 ms 5.503 ms 8 if-9-5.tcore1.WYN-Marseille.as6453.net (80.231.217.17) 216.909 ms 198.864 ms 201.737 ms 9 if-2-2.tcore2.WYN-Marseille.as6453.net (80.231.217.2) 203.305 ms 203.141 ms 202.888 ms10 if-5-2.tcore1.WV6-Madrid.as6453.net (80.231.200.6) 200.552 ms 202.463 ms 202.222 ms11 if-8-2.tcore2.SV8-Highbridge.as6453.net (80.231.91.26) 205.446 ms 215.885 ms 202.867 ms12 if-2-2.tcore1.SV8-Highbridge.as6453.net (80.231.139.2) 202.675 ms 201.540 ms 203.972 ms13 if-6-2.tcore1.NJY-Newark.as6453.net (80.231.138.18) 203.732 ms 203.496 ms 202.951 ms14 if-2-2.tcore2.NJY-Newark.as6453.net (66.198.70.2) 203.858 ms 203.373 ms 203.208 ms15 66.198.111.26 (66.198.111.26) 201.093 ms 63.243.128.25 (63.243.128.25) 206.597 ms 66.198.111.26 (66.198.111.26) 204.178 ms16 ae9.edge1.NewYork.Level3.net (4.68.62.185) 205.960 ms 205.740 ms 205.487 ms17 vlan51.ebr1.NewYork2.Level3.net (4.69.138.222) 203.867 ms vlan52.ebr2.NewYork2.Level3.net (4.69.138.254) 202.850 ms vlan51.ebr1.NewYork2.Level3.net (4.69.138.222) 202.351 ms18 ae-6-6.ebr2.NewYork1.Level3.net (4.69.141.21) 201.771 ms 201.185 ms 201.120 ms19 ae-81-81.csw3.NewYork1.Level3.net (4.69.134.74) 202.407 ms 201.479 ms ae-92-92.csw4.NewYork1.Level3.net (4.69.148.46) 208.145 ms20 ae-2-70.edge2.NewYork1.Level3.net (4.69.155.80) 200.572 ms ae-4-90.edge2.NewYork1.Level3.net (4.69.155.208) 200.402 ms ae-1-60.edge2.NewYork1.Level3.net (4.69.155.16) 203.573 ms21 b.resolvers.Level3.net (4.2.2.2) 199.725 ms 199.190 ms 202.488 ms
4. Netstat Command
Netstat (Network Statistic) command displays connection info, routing table information, etc. To display routing table information use option as-r.
# netstat -rKernel IP routing tableDestination Gateway Genmask Flags MSS Window irtt Iface192.168.50.0 * 255.255.255.0 U 0 0 0 eth0link-local * 255.255.0.0 U 0 0 0 eth0default 192.168.50.1 0.0.0.0 UG 0 0 0 eth0
For more examples ofNetstat Command, please read our earlier article on20 Netstat Command Examples in Linux.
Update: Thenetstat command is replaced by thess (socket statistics) command in most modern Linux distributions.
5. Dig Command
Dig (domain information groper) queryDNS related information likeA Record,CNAME,MX Record, etc. This command is mainly used to troubleshootDNS-related queries.
# dig www.tecmint.com; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.10.rc1.el6 <<>> www.tecmint.com;; global options: +cmd;; Got answer:;; ->>HEADER<
For more examples ofDig Command, please read the article on10 Linux Dig Commands to Query DNS.
6. Nslookup Command
nslookup command is also used to find outDNS-related queries. The following examples showA Record (IP Address) oftecmint.com.
# nslookup www.tecmint.comServer: 4.2.2.2Address: 4.2.2.2#53Non-authoritative answer:www.tecmint.com canonical name = tecmint.com.Name: tecmint.comAddress: 50.116.66.136
For moreNslookup Command, read the article on8 Linux Nslookup Command Examples.
7. Route Command
route command also shows and manipulates theip routing table. To see the default routing table inLinux, type the following command.
# routeKernel IP routing tableDestination Gateway Genmask Flags Metric Ref Use Iface192.168.50.0 * 255.255.255.0 U 0 0 0 eth0link-local * 255.255.0.0 U 1002 0 0 eth0default 192.168.50.1 0.0.0.0 UG 0 0 0 eth0
Adding, deleting routes and default Gateway with following commands.
Add Route in Linux
# route add -net 10.10.10.0/24 gw 192.168.0.1
Delete Route in Linux
# route del -net 10.10.10.0/24 gw 192.168.0.1
Add Default Gateway in Linux
# route add default gw 192.168.0.1
8. Host Command
host command to find a name toIP orIP to name inIPv4 orIPv6 and also queryDNS records.
# host www.google.comwww.google.com has address 173.194.38.180www.google.com has address 173.194.38.176www.google.com has address 173.194.38.177www.google.com has address 173.194.38.178www.google.com has address 173.194.38.179www.google.com has IPv6 address 2404:6800:4003:802::1014
Using-t an option to find out DNS Resource Records likeCNAME,NS,MX,SOA, etc.
# host -t CNAME www.redhat.comwww.redhat.com is an alias for wildcard.redhat.com.edgekey.net.
9. Arp Command
ARP (Address Resolution Protocol) is useful toview/add the contents of the kernel’sARP tables. To see the default table use the command as.
# arp -eAddress HWtype HWaddress Flags Mask Iface192.168.50.1 ether 00:50:56:c0:00:08 C eth0
10. Ethtool Command
ethtool is a replacement formii-tool. It is to view, setting speed and duplex of yourNetwork Interface Card(NIC). You can set duplex permanently in/etc/sysconfig/network-scripts/ifcfg-eth0 withETHTOOL_OPTS variable.
# ethtool eth0Settings for eth0: Current message level: 0x00000007 (7) Link detected: yes
11. Iwconfig Command
iwconfig command inLinux is used to configure awireless network interface. You can see and set the basicWi-Fi details likeSSID channel and encryption. You can refer man page ofiwconfig to know more.
# iwconfig [interface]
12. Hostname Command
Thehostname is to identify in a network. Execute thehostname 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 tecmint.com
13. Nmcli and Nmtui Tools
TheNmcli andNmtui tools are used to configure network settings and also used to manage network devices, create, modify, activate/deactivate, and delete network connections in Linux systems.
# nmcli# nmtui
This article can be useful for day to day use ofLinux Network administrators inLinux / Unix-like operating systems. Kindly share through our comment box if we missed out.
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56 Comments
Leave a ReplyWhy does the Tecmint staff insist on prefixing all their sample command in all their articles with a hash mark
Reply(#)? Commands written in this way will be treated as comments by the Linux Operating System and never be executed.dns is replying fine but internet is not working in Ubuntu.
Replysystem-config-network doesn’t work on my KDE Neon
ReplyThis article is so out of date that it should be removed. In particular, use the ip command and use tracepath, not traceroute.
ReplyIt is a bit out of date, sure, but these commands still work.traceroute is still usable, and pathping is ICMP, it is not the same underlying protocol as traceroute. It’s always easy to criticize. The author might not be an authoritative person for Linux administration, maybe just someone sharing their thoughts
Reply
Excellent list, all commands are very useful.
Replysome command not working on kali
Replygive me full command list bro
ReplyI need information about “Write a short note on troubleshooting in Linux”
ReplyI have interview in linux I am fresher they ask me to prepare network commands.
Reply
Is this enough for that as you taught above!!!What would you recommend for a Certified Linux technician, with no experience on Linux OS. I would like to get more experience on useful commands and how to navigate in and out through network settings for servers.
Reply@Moe,
I recommend you to first learn the basics of Linux (command and usage) and then dive into more advance level, it will help you to enhance your skills on Linux, Here is the complete noob guide for Linux, go through it as per their order and learn it on your own way….
https://www.tecmint.com/free-online-linux-learning-guide-for-beginners/
Reply
This is very very usefull
Replyvery useful
Replythis is very usefull ,thanx
ReplyI would add tcpdump and wire shark for sniffing packets
Reply
Traceroute is good as wellKernel bypass networking is increasing reputation. This depicts affecting organize of Ethernet hardware straight into user space procedures to evade the transparency of con-terminal with the operating system Kernel.
ReplyAre those tools used for system configuration?
Replyoverall the content is good
Replywill u please give the clear information regarding the nslookup command in linux
ReplyThanks for the comprehensive definitions and examples.
ReplyHi
if I set up a VPN to a server using Windows, I am able to ping to the server (192.168.1.1) AND to a desktop in the server network (i.e. 192.168.1.221). When I do the same under Linux I can ping to the server, but not anymore to the desktop linked to the server (i.e. 192.168.1.221).
Any suggestion what tool I could use to discover the problem?
Gert
Replyif i use ndis wrapper to install my wireless driver in Centos 6.5 an i can’t find a record which identify my wireless driver and i can’t find a record in /etc/sysconfig/network-scripts which show me lo and eth0 only !!!!!!!!
Replyi want to know what is the command for inseting data into existing file in anyware instead of vi editor
pls let me know
Replywhich is the program that contains the package “system-config-network” ??
Replywhat is the command in Linux to find traffic between to IPS … i.e Source IP and Destination IP
ReplyI believe ping is the “packet internet groper”, not “gopher” as indicated
Replywe are not able to ping the gateway ip. how can i check this. can you please advice me.
ReplyHello,
Do you happen to know how to delete my router details on linux and start again? As in a way that the router could not recognize my device unless I manually take care of that.
We’re having kind of network issues because the router is “confused” because it doesn’t know which Ip address to go to since it has been configurated since the very beginning on two laptops while it actually is alloud on one. SOrry for my bad English. Looking forward for your reply.
Thanks!Adelina
Replyover all information is good
ReplyCould you also go through some commands which show hardware and driver details?
ReplyHey… can we down the interface using “system-config-network” command?
Reply
If yes how?ifconfig, route, and netstat are deprecated so you might want to rewrite your howto substituting ip and ss
ReplySorry, but according to this posthttps://dougvitale.wordpress.com/2011/12/21/deprecated-linux-networking-commands-and-their-replacements/ many of the commands you’ve listed here are deprecated.
ReplyHasn’t ifconfig been deprecated and replaced by the ip command?
ReplyInformative article, Thank you.
Reply