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| + | ====== Commonly Used Network Commands / Tools ====== | ||
| + | ===== Define DNS Servers ===== | ||
| + | Add/update DNS Server configurations in /etc/resolv.conf in the format ''nameserver <IP-Address>'', one for each line. The /etc/resolve.conf file //does// get overwritten each time the system is rebooted. In Ububtu the /etc/resolvconf/resolv.conf.d/head is the source file and updating it keeps the changes permanent. In distros (such as Redhat) you can make the /etc/resolv.conf file read-only by ''chattr +i /etc/resolv.conf''. Use the ''-i'' option to make the file read-write again. By default, the default gateway resolves DNS. | ||
| + | |||
| + | ===== LISTEN address list ===== | ||
| + | netstat Command to list LISTEN addresses (listening ports) | ||
| + | <code bash> | ||
| + | netstat -pnutl | ||
| + | netstat -pnutl | grep :80 | ||
| + | </code> | ||
| + | |||
| + | |||
| + | Processes PID that opened tcp port 80 (run as root): | ||
| + | <code bash> | ||
| + | fuser 80/tcp | ||
| + | fuser -u -v 80/tcp | ||
| + | </code> | ||
| + | Sample output: | ||
| + | <code> | ||
| + | 80/tcp: 1741 7842 11760 14459 | ||
| + | </code> | ||
| + | |||
| + | Process name associated with PID # | ||
| + | <code bash>ls -l /proc/1741/exe</code> | ||
| + | |||
| + | ===== Display Network Interface Statistics ===== | ||
| + | <code bash> | ||
| + | netstat -i | ||
| + | </code> | ||
| + | |||
| + | ===== Create a LISTEN address ===== | ||
| + | nc Command to Create a service using bash script (to listen on port 8444 for example) | ||
| + | <code bash> | ||
| + | nc -k -l 8444 | ||
| + | </code> | ||
| + | Keywords: Listener socket server bash bind TCP netcat\\ | ||
| + | Resources: [[http://stackoverflow.com/questions/4739196/simple-socket-server-in-bash|Simple Socket Server in Bash]] | ||
| + | |||
| + | |||
| + | ===== To send to a LISTEN address ===== | ||
| + | Target IP is the IP address of the server running ''nc -k -l 8444'' and waiting on requests. | ||
| + | <code bash> | ||
| + | echo "test-hello" | nc <target-ip> 8444 | ||
| + | </code> | ||
| + | |||
| + | |||
| + | ===== Find systems without ping ===== | ||
| + | Some servers/devices have ping (ICMP) disabled. In that case use arping to find them. Example use below. | ||
| + | <code bash> | ||
| + | arping -c1 -f -w1 192.168.1.1 | ||
| + | </code> | ||
| + | ==== arping usage help ==== | ||
| + | <code> | ||
| + | Usage: arping [-fqbDUAV] [-c count] [-w timeout] [-I device] [-s source] destination | ||
| + | -f : quit on first reply | ||
| + | -q : be quiet | ||
| + | -b : keep broadcasting, don't go unicast | ||
| + | -D : duplicate address detection mode | ||
| + | -U : Unsolicited ARP mode, update your neighbours | ||
| + | -A : ARP answer mode, update your neighbours | ||
| + | -V : print version and exit | ||
| + | -c count : how many packets to send | ||
| + | -w timeout : how long to wait for a reply | ||
| + | -I device : which ethernet device to use (eth0) | ||
| + | -s source : source ip address | ||
| + | destination : ask for what ip address | ||
| + | </code> | ||
| + | |||
| + | ===== Find open ports ===== | ||
| + | nmap can be used to find open ports. Simple example below: | ||
| + | <code bash> | ||
| + | nmap 192.168.1.1 | ||
| + | </code> | ||
| + | |||
| + | Also ''nc'' can be used to find if a port is open | ||
| + | <code> | ||
| + | nc -zv 192.168.1.100 80 | ||
| + | </code> | ||
| + | |||
| + | On Windows | ||
| + | <code bat> | ||
| + | PowerShell | ||
| + | Test-NetConnection -ComputerName 192.168.1.21 -Port 22 | ||
| + | </code> | ||
