Saturday, 29 August 2015

RHEL7 Linux Network Configuration and Troubleshooting CLI Commands

After this article you can able to manage Network interface effectively and you simple troubleshoot.

 STEP1: To check the server IP Address

Command 'ifconfig' will show you IP address of all the Ethernet interfaces. Above command will work in RHEL 4/5/6/7 versions.

~]#ifconfig ens33 

If you specify Ethernet device name then it will show the details of that particular device only.

 ~]#ip addr show

above command will work in RHEL 7 version , it not works in below RHEL7 version. it is also same as 'ifconfig' in previous versions.

~]#ip addr show ens33

 Specify the Network device name will show only that particular device details.

STEP 2: Assign IP Address

 ~]# nmtui
    NetworkManager text user interface (TUI) tool,  nmtui, provides a text interface to configure networking by controlling NetworkManager.


"Select Edit a connection" option if you want to change the IP / Assign the IP

Select the Interface name if you have multiple interfaces select it carefully

 click on OK.

Then restart the Network services by entering below command
 ~]# systemctl restart network
 ~]# systemctl status network

 Restart/reaload the service to effect the new changes

Do not run any service by calling /etc/init.d/servicename start|stop|restart|status directly.

    Note that in Red Hat Enterprise Linux 7, NetworkManager is started first, and /etc/init.d/network checks with NetworkManager to avoid tampering with NetworkManager's connections. NetworkManager is intended to be the primary application using sysconfig configuration files and /etc/init.d/network is intended to be secondary, playing a fallback role.  

 You can also edit the /etc/sysconfig/network-scripts/ifcfg-ens33 file to Assign/Modify the IP Address.


STEP 3: Bring UP / Bring DOWN the interfaces

~]#ifup interface-name 
~]#ifdown interface-name
~]#nmcli dev disconnect  interface-name
~]#nmcli dev up interface-name

To bring down the interface you can use 'nmcli dev disconnect interface-name' and 'ifdown interface-name'

To bring up the interface you can use 'nmcli con up interface-name' and 'ifup interface-name'

~]#nmcli connection reload

To reaload the interface configuration

Verify the Routing Table

~]#netstat -r

 To see the default routing table above command is useful

 Trace the device path

 ~]#traceroute <IP Address>
 To Trace the network route path traceroute command is useful

 Verify Interface Status and Banwidth Speed

 ~]#ethtool interface-name
 You can verify the interface status and bandwidth using above command.

Find out Host IP Address and CNAME in Domain

 ~]#host host-name
 ~]# host -t a localhost

 to find host IP address and its domain name above command is useful
~]# host -t cname localhost
find out domain cname record 

Check DNS resolution

~]# nslookup IP-Address
~]# dig IP-Address


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