Network Utils

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Count the number of connections

netstat -ant | awk '{print $6}' | sort | uniq -c | sort -n

verify connectivity

  • nslookup myexampledb.xxxx.us-east-1.rds.amazonaws.com
  • telnet <RDS endpoint> <port number>


network traffic by-process

sudo tcpdump -k NP | grep Sublime

check that a node is pingable in bash

while ! ping -c1 bjjc_spec_22.ubuntu14 &>/dev/null; do :; done ;

how do I know if the system trusts the certificate?

you use curl

how to tell if port 80 is listening? What is listening on a particular port?

netstat -plnt
netstat -tunlp
lsof -nP -i4TCP:$PORT | grep LISTEN
lsof -i:1433


netstat -an -ptcp | grep LISTEN

Port Forward

ncat --sh-exec "ncat 10.0.1.117 22" -l 2289
ssh -L 8080:127.0.0.1:8080 -L 8081:127.0.0.1:8081 developer@133.111.111.111

What's running on my ports?

sudo netstat -ltnp
netstat -anp | grep :443 | grep LISTEN

or

 lsof -i -P -n | grep LISTEN

Rename a wireless interface

ip link set wlp5s0 name wlan0

Security

List nodes in the network:

sudo arp-scan -l --interface=wlan0

This is better than wireshark and tcpdump:

ngrep port 3000
ngrep -d any -W byline port 5000

Troubleshoot

RTNETLINK answers: File exists

 sudo ip addr flush dev wlan0