{"id":12110,"date":"2019-03-22T10:32:00","date_gmt":"2019-03-22T10:32:00","guid":{"rendered":"http:\/\/www.appservgrid.com\/paw92\/?p=12110"},"modified":"2019-03-22T10:32:33","modified_gmt":"2019-03-22T10:32:33","slug":"13-linux-network-configuration-and-troubleshooting-commands","status":"publish","type":"post","link":"https:\/\/www.appservgrid.com\/paw92\/index.php\/2019\/03\/22\/13-linux-network-configuration-and-troubleshooting-commands\/","title":{"rendered":"13 Linux Network Configuration and Troubleshooting Commands"},"content":{"rendered":"

Computers are connected in a network to exchange information or resources each other. Two or more computer connected through network media called\u00a0computer network<\/strong>. There are number of network devices or media are involved to form computer network. Computer loaded with\u00a0Linux Operating System<\/strong>\u00a0can also be a part of network whether it is small or large network by its\u00a0multitasking and multiuser<\/strong>\u00a0natures. Maintaining of system and network up and running is a task of\u00a0System \/ Network Administrator\u2019s<\/strong>\u00a0job. In this article we are going to review frequently used network configuration and troubleshoot commands in Linux.<\/p>\n

\n

\"Linux<\/a><\/p>\n

Linux Network Configuration and Troubleshooting Commands<\/p>\n<\/div>\n

1. ifconfig<\/h3>\n

ifconfig<\/strong>\u00a0(interface configurator<\/strong>) command is use to initialize an interface, assign\u00a0IP Address<\/strong>\u00a0to interface and\u00a0enable<\/strong>\u00a0or\u00a0disable<\/strong>\u00a0interface on demand. With this command you can view\u00a0IP Address<\/strong>\u00a0and\u00a0Hardware<\/strong>\u00a0\/\u00a0MAC address<\/strong>\u00a0assign to interface and also\u00a0MTU<\/strong>\u00a0(Maximum transmission unit<\/strong>) size.<\/p>\n

# ifconfig<\/strong>\r\n\r\neth0      Link encap:Ethernet  HWaddr 00:0C:29:28:FD:4C<\/strong>\r\n          inet addr:192.168.50.2<\/strong>  Bcast:192.168.50.255  Mask:255.255.255.0\r\n          inet6 addr: fe80::20c:29ff:fe28:fd4c\/64 Scope:Link\r\n          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1\r\n          RX packets:6093 errors:0 dropped:0 overruns:0 frame:0\r\n          TX packets:4824 errors:0 dropped:0 overruns:0 carrier:0\r\n          collisions:0 txqueuelen:1000\r\n          RX bytes:6125302 (5.8 MiB)  TX bytes:536966 (524.3 KiB)\r\n          Interrupt:18 Base address:0x2000\r\n\r\nlo        Link encap:Local Loopback\r\n          inet addr:127.0.0.1  Mask:255.0.0.0\r\n          inet6 addr: ::1\/128 Scope:Host\r\n          UP LOOPBACK RUNNING  MTU:16436  Metric:1\r\n          RX packets:8 errors:0 dropped:0 overruns:0 frame:0\r\n          TX packets:8 errors:0 dropped:0 overruns:0 carrier:0\r\n          collisions:0 txqueuelen:0\r\n          RX bytes:480 (480.0 b)  TX bytes:480 (480.0 b)<\/pre>\n
ifconfig<\/strong>\u00a0with interface (eth0<\/strong>) command only shows specific interface details like\u00a0IP Address<\/strong>,\u00a0MAC Address<\/strong>\u00a0etc. with\u00a0-a<\/strong>\u00a0options will display all available interface details if it is disable also.<\/p>\n
# ifconfig eth0<\/strong>\r\n\r\neth0      Link encap:Ethernet  HWaddr 00:0C:29:28:FD:4C\r\n          inet addr:192.168.50.2  Bcast:192.168.50.255  Mask:255.255.255.0\r\n          inet6 addr: fe80::20c:29ff:fe28:fd4c\/64 Scope:Link\r\n          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1\r\n          RX packets:6119 errors:0 dropped:0 overruns:0 frame:0\r\n          TX packets:4841 errors:0 dropped:0 overruns:0 carrier:0\r\n          collisions:0 txqueuelen:1000\r\n          RX bytes:6127464 (5.8 MiB)  TX bytes:539648 (527.0 KiB)\r\n          Interrupt:18 Base address:0x2000<\/pre>\n
Assigning IP Address and Gateway<\/h4>\n
Assigning an\u00a0IP Address<\/strong>\u00a0and\u00a0Gateway<\/strong>\u00a0to interface on the fly. The setting will be removed in case of system reboot.<\/p>\n
# ifconfig eth0 192.168.50.5 netmask 255.255.255.0<\/strong><\/pre>\n
Enable or Disable Specific Interface<\/h4>\n
To\u00a0enable<\/strong>\u00a0or\u00a0disable<\/strong>\u00a0specific Interface, we use example command as follows.<\/p>\n
Enable eth0<\/h5>\n
# ifup eth0<\/strong><\/pre>\n
Disable eth0<\/h5>\n
# ifdown eth0<\/strong><\/pre>\n
Setting MTU Size<\/h4>\n
By default\u00a0MTU<\/strong>\u00a0size is\u00a01500<\/strong>. We can set required\u00a0MTU<\/strong>\u00a0size with below command. Replace\u00a0XXXX<\/strong>\u00a0with size.<\/p>\n
# ifconfig eth0 mtu XXXX<\/strong><\/pre>\n
Set Interface in Promiscuous mode<\/h4>\n
Network interface<\/strong>\u00a0only received packets belongs to that particular\u00a0NIC<\/strong>. If you put interface in\u00a0promiscuous<\/strong>mode it will received all the packets. This is very useful to capture packets and analyze later. For this you may require superuser access.<\/p>\n
# ifconfig eth0 - promisc<\/strong><\/pre>\n
2. PING Command<\/h3>\n
PING<\/strong>\u00a0(Packet INternet Groper<\/strong>) command is the best way to test connectivity between\u00a0two nodes<\/strong>. Whether it is\u00a0Local Area Network<\/strong>\u00a0(LAN<\/strong>) or\u00a0Wide Area Network<\/strong>\u00a0(WAN<\/strong>). Ping use\u00a0ICMP<\/strong>\u00a0(Internet Control Message Protocol<\/strong>) to communicate to other devices. You can ping host name of\u00a0ip address<\/strong>\u00a0using below command.<\/p>\n
# ping 4.2.2.2<\/strong>\r\n\r\nPING 4.2.2.2 (4.2.2.2) 56(84) bytes of data.\r\n64 bytes from 4.2.2.2: icmp_seq=1 ttl=44 time=203 ms\r\n64 bytes from 4.2.2.2: icmp_seq=2 ttl=44 time=201 ms\r\n64 bytes from 4.2.2.2: icmp_seq=3 ttl=44 time=201 ms\r\n\r\nOR\r\n\r\n# ping www.tecmint.com<\/strong>\r\n\r\nPING tecmint.com (50.116.66.136) 56(84) bytes of data.\r\n64 bytes from 50.116.66.136: icmp_seq=1 ttl=47 time=284 ms\r\n64 bytes from 50.116.66.136: icmp_seq=2 ttl=47 time=287 ms\r\n64 bytes from 50.116.66.136: icmp_seq=3 ttl=47 time=285 ms<\/pre>\n
In\u00a0Linux<\/strong>\u00a0ping command keep executing until you interrupt. Ping with\u00a0-c<\/strong>\u00a0option exit after\u00a0N<\/strong>\u00a0number of request (success or error respond).<\/p>\n
# ping -c 5 www.tecmint.com<\/strong>\r\n\r\nPING tecmint.com (50.116.66.136) 56(84) bytes of data.\r\n64 bytes from 50.116.66.136: icmp_seq=1 ttl=47 time=285 ms\r\n64 bytes from 50.116.66.136: icmp_seq=2 ttl=47 time=285 ms\r\n64 bytes from 50.116.66.136: icmp_seq=3 ttl=47 time=285 ms\r\n64 bytes from 50.116.66.136: icmp_seq=4 ttl=47 time=285 ms\r\n64 bytes from 50.116.66.136: icmp_seq=5 ttl=47 time=285 ms\r\n\r\n--- tecmint.com ping statistics ---\r\n5 packets transmitted, 5 received, 0% packet loss, time 4295ms\r\nrtt min\/avg\/max\/mdev = 285.062\/285.324\/285.406\/0.599 ms<\/pre>\n
3. TRACEROUTE Command<\/h3>\n
traceroute<\/strong>\u00a0is 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\u00a0DNS server IP Address<\/strong>\u00a0and able to reach destination also shows path of that packet is traveling.<\/p>\n
# traceroute 4.2.2.2<\/strong>\r\n\r\ntraceroute to 4.2.2.2 (4.2.2.2), 30 hops max, 60 byte packets\r\n 1  192.168.50.1 (192.168.50.1)  0.217 ms  0.624 ms  0.133 ms\r\n 2  227.18.106.27.mysipl.com (27.106.18.227)  2.343 ms  1.910 ms  1.799 ms\r\n 3  221-231-119-111.mysipl.com (111.119.231.221)  4.334 ms  4.001 ms  5.619 ms\r\n 4  10.0.0.5 (10.0.0.5)  5.386 ms  6.490 ms  6.224 ms\r\n 5  gi0-0-0.dgw1.bom2.pacific.net.in (203.123.129.25)  7.798 ms  7.614 ms  7.378 ms\r\n 6  115.113.165.49.static-mumbai.vsnl.net.in (115.113.165.49)  10.852 ms  5.389 ms  4.322 ms\r\n 7  ix-0-100.tcore1.MLV-Mumbai.as6453.net (180.87.38.5)  5.836 ms  5.590 ms  5.503 ms\r\n 8  if-9-5.tcore1.WYN-Marseille.as6453.net (80.231.217.17)  216.909 ms  198.864 ms  201.737 ms\r\n 9  if-2-2.tcore2.WYN-Marseille.as6453.net (80.231.217.2)  203.305 ms  203.141 ms  202.888 ms\r\n10  if-5-2.tcore1.WV6-Madrid.as6453.net (80.231.200.6)  200.552 ms  202.463 ms  202.222 ms\r\n11  if-8-2.tcore2.SV8-Highbridge.as6453.net (80.231.91.26)  205.446 ms  215.885 ms  202.867 ms\r\n12  if-2-2.tcore1.SV8-Highbridge.as6453.net (80.231.139.2)  202.675 ms  201.540 ms  203.972 ms\r\n13  if-6-2.tcore1.NJY-Newark.as6453.net (80.231.138.18)  203.732 ms  203.496 ms  202.951 ms\r\n14  if-2-2.tcore2.NJY-Newark.as6453.net (66.198.70.2)  203.858 ms  203.373 ms  203.208 ms\r\n15  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 ms\r\n16  ae9.edge1.NewYork.Level3.net (4.68.62.185)  205.960 ms  205.740 ms  205.487 ms\r\n17  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 ms\r\n18  ae-6-6.ebr2.NewYork1.Level3.net (4.69.141.21)  201.771 ms  201.185 ms  201.120 ms\r\n19  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 ms\r\n20  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 ms\r\n21  b.resolvers.Level3.net (4.2.2.2)  199.725 ms  199.190 ms  202.488 ms<\/pre>\n
4. NETSTAT Command<\/h3>\n
Netstat<\/strong>\u00a0(Network Statistic<\/strong>) command display connection info, routing table information etc. To displays routing table information use option as\u00a0-r<\/strong>.<\/p>\n
# netstat -r<\/strong>\r\n\r\nKernel IP routing table\r\nDestination     Gateway         Genmask         Flags   MSS Window  irtt Iface\r\n192.168.50.0    *               255.255.255.0   U         0 0          0 eth0\r\nlink-local      *               255.255.0.0     U         0 0          0 eth0\r\ndefault         192.168.50.1    0.0.0.0         UG        0 0          0 eth0<\/pre>\n
For more examples of\u00a0Netstat Command<\/strong>, please read our earlier article on\u00a020 Netstat Command Examples in Linux<\/a>.<\/p>\n
5. DIG Command<\/h3>\n
Dig<\/strong>\u00a0(domain information groper<\/strong>) query\u00a0DNS<\/strong>\u00a0related information like\u00a0A Record<\/strong>,\u00a0CNAME<\/strong>,\u00a0MX Record<\/strong>\u00a0etc. This command mainly use to troubleshoot\u00a0DNS<\/strong>\u00a0related query.<\/p>\n
# dig www.tecmint.com<\/strong>; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.10.rc1.el6 <<>> www.tecmint.com\r\n;; global options: +cmd\r\n;; Got answer:\r\n;; ->>HEADER<<\/pre>\n
For more examples of\u00a0Dig Command<\/strong>, please read the article on\u00a010 Linux Dig Commands to Query DNS<\/a>.<\/p>\n
6. NSLOOKUP Command<\/h3>\n
nslookup<\/strong>\u00a0command also use to find out\u00a0DNS<\/strong>\u00a0related query. The following examples shows\u00a0A Record<\/strong>\u00a0(IP Address<\/strong>) of\u00a0tecmint.com<\/strong>.<\/p>\n
# nslookup www.tecmint.com<\/strong>\r\nServer:         4.2.2.2\r\nAddress:        4.2.2.2#53\r\n\r\nNon-authoritative answer:\r\nwww.tecmint.com canonical name = tecmint.com.\r\nName:   tecmint.com\r\nAddress: 50.116.66.136<\/pre>\n
For more\u00a0NSLOOKUP Command<\/strong>, read the article on\u00a08 Linux Nslookup Command Examples<\/a>.<\/p>\n
7. ROUTE Command<\/h3>\n
route<\/strong>\u00a0command also shows and manipulate\u00a0ip<\/strong>\u00a0routing table. To see default routing table in\u00a0Linux<\/strong>, type the following command.<\/p>\n
# route<\/strong>\r\n\r\nKernel IP routing table\r\nDestination     Gateway         Genmask         Flags Metric Ref    Use Iface\r\n192.168.50.0    *               255.255.255.0   U     0      0        0 eth0\r\nlink-local      *               255.255.0.0     U     1002   0        0 eth0\r\ndefault         192.168.50.1    0.0.0.0         UG    0      0        0 eth0<\/pre>\n
Adding, deleting routes and default Gateway with following commands.<\/p>\n
Route Adding<\/h5>\n
# route add -net 10.10.10.0\/24 gw 192.168.0.1<\/strong><\/pre>\n
Route Deleting<\/h5>\n
# route del -net 10.10.10.0\/24 gw 192.168.0.1<\/strong><\/pre>\n
Adding default Gateway<\/h5>\n
# route add default gw 192.168.0.1<\/strong><\/pre>\n
8. HOST Command<\/h3>\n
host<\/strong>\u00a0command to find name to\u00a0IP<\/strong>\u00a0or\u00a0IP<\/strong>\u00a0to name in\u00a0IPv4<\/strong>\u00a0or\u00a0IPv6<\/strong>\u00a0and also query\u00a0DNS<\/strong>\u00a0records.<\/p>\n
# host www.google.com<\/strong>\r\n\r\nwww.google.com has address 173.194.38.180\r\nwww.google.com has address 173.194.38.176\r\nwww.google.com has address 173.194.38.177\r\nwww.google.com has address 173.194.38.178\r\nwww.google.com has address 173.194.38.179\r\nwww.google.com has IPv6 address 2404:6800:4003:802::1014<\/pre>\n
Using\u00a0-t<\/strong>\u00a0option we can find out DNS Resource Records like\u00a0CNAME<\/strong>,\u00a0NS<\/strong>,\u00a0MX<\/strong>,\u00a0SOA<\/strong>\u00a0etc.<\/p>\n
# host -t CNAME www.redhat.com<\/strong>\r\n\r\nwww.redhat.com is an alias for wildcard.redhat.com.edgekey.net.<\/pre>\n
9. ARP Command<\/h3>\n
ARP<\/strong>\u00a0(Address Resolution Protocol) is useful to\u00a0view<\/strong>\u00a0\/\u00a0add<\/strong>\u00a0the contents of the kernel\u2019s\u00a0ARP tables<\/strong>. To see default table use the command as.<\/p>\n
# arp -e<\/strong>\r\n\r\nAddress                  HWtype  HWaddress           Flags Mask            Iface\r\n192.168.50.1             ether   00:50:56:c0:00:08   C                     eth0<\/pre>\n
10. ETHTOOL Command<\/h3>\n
ethtool<\/strong>\u00a0is a replacement of\u00a0mii-tool<\/strong>. It is to view, setting speed and duplex of your\u00a0Network Interface Card\u00a0<\/strong>(NIC<\/strong>). You can set duplex permanently in\u00a0\/etc\/sysconfig\/network-scripts\/ifcfg-eth0<\/strong>\u00a0with\u00a0ETHTOOL_OPTS<\/strong>\u00a0variable.<\/p>\n
# ethtool eth0<\/strong>\r\n\r\nSettings for eth0:\r\n        Current message level: 0x00000007 (7)\r\n        Link detected: yes<\/pre>\n
11. IWCONFIG Command<\/h3>\n
iwconfig<\/strong>\u00a0command in\u00a0Linux<\/strong>\u00a0is use to configure a\u00a0wireless network interface<\/strong>. You can see and set the basic\u00a0Wi-Fi<\/strong>\u00a0details like\u00a0SSID<\/strong>\u00a0channel and encryption. You can refer man page of\u00a0iwconfig<\/strong>\u00a0to know more.<\/p>\n
# iwconfig [interface]<\/strong><\/pre>\n
12. HOSTNAME Command<\/h3>\n
hostname<\/strong>\u00a0is to identify in a network. Execute\u00a0hostname<\/strong>\u00a0command to see the hostname of your box. You can set hostname permanently in\u00a0\/etc\/sysconfig\/network<\/strong>. Need to reboot box once set a proper hostname.<\/p>\n
# hostname<\/strong> \r\n\r\ntecmint.com<\/pre>\n
13. GUI tool system-config-network<\/h3>\n
Type\u00a0system-config-network<\/strong>\u00a0in command prompt to configure network setting and you will get nice\u00a0Graphical User Interface<\/strong>\u00a0(GUI<\/strong>) which may also use to configure\u00a0IP Address<\/strong>,\u00a0Gateway<\/strong>,\u00a0DNS<\/strong>\u00a0etc. as shown below image.<\/p>\n
# system-config-network<\/strong><\/pre>\n
\n
\"Linux<\/a><\/p>\n
Linux GUI Network Configuration Tool<\/p>\n<\/div>\n
This article can be useful for day to day use of\u00a0Linux Network administrator<\/strong>\u00a0in\u00a0Linux<\/strong>\u00a0\/ Unix-like operating system. Kindly share through our comment box if we missed out.<\/p>\n
Source<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"
Computers are connected in a network to exchange information or resources each other. Two or more computer connected through network media called\u00a0computer network. There are number of network devices or media are involved to form computer network. Computer loaded with\u00a0Linux Operating System\u00a0can also be a part of network whether it is small or large network … <\/p>\n
Continue reading “13 Linux Network Configuration and Troubleshooting Commands”<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-12110","post","type-post","status-publish","format-standard","hentry","category-linux"],"_links":{"self":[{"href":"https:\/\/www.appservgrid.com\/paw92\/index.php\/wp-json\/wp\/v2\/posts\/12110","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.appservgrid.com\/paw92\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.appservgrid.com\/paw92\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.appservgrid.com\/paw92\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.appservgrid.com\/paw92\/index.php\/wp-json\/wp\/v2\/comments?post=12110"}],"version-history":[{"count":2,"href":"https:\/\/www.appservgrid.com\/paw92\/index.php\/wp-json\/wp\/v2\/posts\/12110\/revisions"}],"predecessor-version":[{"id":12112,"href":"https:\/\/www.appservgrid.com\/paw92\/index.php\/wp-json\/wp\/v2\/posts\/12110\/revisions\/12112"}],"wp:attachment":[{"href":"https:\/\/www.appservgrid.com\/paw92\/index.php\/wp-json\/wp\/v2\/media?parent=12110"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.appservgrid.com\/paw92\/index.php\/wp-json\/wp\/v2\/categories?post=12110"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.appservgrid.com\/paw92\/index.php\/wp-json\/wp\/v2\/tags?post=12110"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}