TO resolve network related issue/connection issue in linux server, some commands are so much helpful.
• finding host/domain name and IP address - hostname
• test network connection – ping
• getting network configuration – ifconfig
• Network connections, routing tables, interface statistics – netstat
• query DNS lookup name – nslookup
• communicate with other hostname – telnet
• outing steps that packets take to get to network host – traceroute
• view user information – finger
• checking status of destination host - telnet
hostname
hostname with no options displays the machines host name
hostname –i displays the IP address for the current machine
hostname –d displays the domain name the machine belongs to
hostname –f displays the fully qualified host and domain name
ping
It sends packets of information to the user-defined source. If the packets are received, the destination device sends packets back. Ping can be used for two purposes
1. To ensure that a network connection can be established.
2. Timing information as to the speed of the connection.
If you do ping www.google.com it will display its IP address. Use ctrl+C to stop the test.
ifconfig
View network configuration, it displays the current network adapter configuration. It is handy to determine if you are getting transmit (TX) or receive (RX) errors.
netstat
Most useful and very versatile for finding connection to and from the host. You can find out all the multicast groups (network) subscribed by this host by issuing "netstat -g"
netstat -nap | grep port will display process id of application which is using that port
netstat -a or netstat –all will display all connections including TCP and UDP
netstat --tcp or netstat –t will display only TCP connection
netstat --udp or netstat –u will display only UDP connection
netstat -g will display all multicast network subscribed by this host.
nslookup
If you know the IP address it will display hostname. To find all the IP addresses for a given domain name, the command nslookup is used.
You can also use nslookup to convert hostname to IP Address and from IP Address from hostname.
traceroute
A handy utility to view the number of hops and response time to get to a remote system or web site is traceroute. Again you need an internet connection to make use of this tool.
finger
View user information, displays a user’s login name, real name, terminal name and write status. this is pretty old unix command and rarely used now days.
In ubuntu finger package is not installed by default. To install that, we need to install that using command:
sudo apt-get install finger
telnet
Connects destination host via telnet protocol, if telnet connection establish on any port means connectivity between two hosts is working fine.
telnet hostname port will telnet hostname with the port specified. Normally it is used to see whether host is alive and network connection is fine or not.
• finding host/domain name and IP address - hostname
• test network connection – ping
• getting network configuration – ifconfig
• Network connections, routing tables, interface statistics – netstat
• query DNS lookup name – nslookup
• communicate with other hostname – telnet
• outing steps that packets take to get to network host – traceroute
• view user information – finger
• checking status of destination host - telnet
hostname
hostname with no options displays the machines host name
hostname –i displays the IP address for the current machine
hostname –d displays the domain name the machine belongs to
hostname –f displays the fully qualified host and domain name
ping
It sends packets of information to the user-defined source. If the packets are received, the destination device sends packets back. Ping can be used for two purposes
1. To ensure that a network connection can be established.
2. Timing information as to the speed of the connection.
If you do ping www.google.com it will display its IP address. Use ctrl+C to stop the test.
ifconfig
View network configuration, it displays the current network adapter configuration. It is handy to determine if you are getting transmit (TX) or receive (RX) errors.
netstat
Most useful and very versatile for finding connection to and from the host. You can find out all the multicast groups (network) subscribed by this host by issuing "netstat -g"
netstat -nap | grep port will display process id of application which is using that port
netstat -a or netstat –all will display all connections including TCP and UDP
netstat --tcp or netstat –t will display only TCP connection
netstat --udp or netstat –u will display only UDP connection
netstat -g will display all multicast network subscribed by this host.
nslookup
If you know the IP address it will display hostname. To find all the IP addresses for a given domain name, the command nslookup is used.
You can also use nslookup to convert hostname to IP Address and from IP Address from hostname.
traceroute
A handy utility to view the number of hops and response time to get to a remote system or web site is traceroute. Again you need an internet connection to make use of this tool.
finger
View user information, displays a user’s login name, real name, terminal name and write status. this is pretty old unix command and rarely used now days.
In ubuntu finger package is not installed by default. To install that, we need to install that using command:
sudo apt-get install finger
telnet
Connects destination host via telnet protocol, if telnet connection establish on any port means connectivity between two hosts is working fine.
telnet hostname port will telnet hostname with the port specified. Normally it is used to see whether host is alive and network connection is fine or not.
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