Commands tagged networking (37)
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Real gurus don't need fancy tools like iftop or jnettop. Show Sample Output
9tcpdump -w - |pv -bert >/dev/null -
While `lsof` will work, why not use the tool designed explicitly for this job? (If not run as root, you will only see the names of PID you own) Show Sample Output
8netstat -plnt -
6nmap --iflist
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Since systemd-resolved was implemented, add a DNS server have become weirder and harder than before. With this command, you can add a DNS server on-the-fly tied to an specific interface
5sudo systemd-resolve --interface <NombreInterfaz> --set-dns <IPDNS> --set-domain mydomain.com -
see http://iptraf.seul.org/ for all kinds of documentation and screenshots
4iptraf -
4lsof -Pn | grep LISTEN
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Binding a server to privileged port on Linux w/o running as root This is applicable to any service using privileged ports (< 1024), for instance to run a HTTP server on port 80 or a LDAP directory server on port 389 for example. Show Sample Output
4sudo setcap CAP_NET_BIND_SERVICE=+eip /usr/bin/python2.7 -
3nmcli device wifi list
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on multihomed hosts, connected to several networks, could be usefull to know the source address (local ip address) used to reach the target host, this command does not require root priviledges. The command use a TCP socket, if there is any error the command return an empty string, elsewhere return a valid ip address. Show Sample Output
2python -c 'import socket; s = socket.socket(socket.AF_INET, socket.SOCK_STREAM); s.connect(("<hostname>", <port>)); print s.getsockname()[0] ; s.close() ;' 2> /dev/null -
Sometimes, you don't really care about all the other information that ifconfig spits at you (however useful it may otherwise be). You just want an IP. This strips out all the crap and gives you exactly what you want. Show Sample Output
2ifconfig eth1 | grep inet\ addr | awk '{print $2}' | cut -d: -f2 | sed s/^/eth1:\ /g -
2curl -s http://standards.ieee.org/regauth/oui/oui.txt | grep $1
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Sometimes it's useful to output just the ip address. Or some other information, changing the "ipv4.addresses" in command. The power of awk! Show all possible "greps" with
nmcli connection show [yourInterfaceNameHere]Show Sample Output2showip() { nmcli connection show $1|grep ipv4.addresses|awk '{print $2}' ; } -
This command only check the network connection from given eth. This is very useful if you are using more then one interface in your server or laptop. Show Sample Output
1ping -I eth0 www.yahoo.com -
Check open TCP and UDP ports Show Sample Output
1netstat -plntu -
TCP Connect scanning for localhost and network 192.168.0.0/24 Show Sample Output
1nmap -v -sT 192.168.0.0/24 -
This forces a bonded interface to switch to another slave in the bond as its active slave.
1/sbin/ifenslave -c bond0 eth1 -
1watch -n1 iptables -vnL
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Checks whether IPv6 is enabled system-wide by reading from procfs. Show Sample Output
1printf "IPv6 is "; [ $(cat /proc/sys/net/ipv6/conf/all/disable_ipv6) -eq 0 ] && printf "enabled\n" || printf "disabled\n" -
the command for the impatient sysadmin: simply checks every five secs, if a host or a specific service running on it is up. ideal for hosts that are configured not to respond on pings. Show Sample Output
0while true; do clear; nmap ${hostname} -PN -p ${hostport}; sleep 5; done -
This is an commandline utility to get fair piece of information about the attached network card. Show Sample Output
0ethtool eth0 -
Works only on Linux. Last option (n) turn name of service resolving (/etc/services) off. Show Sample Output
0netstat -ltun -
0tcpdump -i any -n tcp[13] == 2
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shows opened ports on machine in continuous mode (refreshing every 10 sec) Show Sample Output
0netstat -tulpnc -
Disabling an interface's multicast filter is like disabling IGMP snooping on a switch. It is useful for testing and troubleshooting.
0ifconfig eth0 allmulti -
Super fast way to ftp/telnet/netcat/ssh/ping your loopback address for testing. The default route 0.0.0.0 is simply reduced to 0. Show Sample Output
0telnet 0 <port> - 1 2 >
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