Network Utils
From Wasya Wiki
Contents
- 1 ubuntu static ip
- 2 Q&A
- 2.1 Count the number of connections
- 2.2 verify connectivity
- 2.3 network traffic by-process
- 2.4 check that a node is pingable in bash
- 2.5 how do I know if the system trusts the certificate?
- 2.6 how to tell if port 80 is listening? What is listening on a particular port?
- 2.7 Port Forward
- 2.8 What's running on my ports?
- 2.9 Rename a wireless interface
- 2.10 Security
- 3 Troubleshoot
ubuntu static ip
From: https://vitux.com/how-to-configure-networking-with-netplan-on-ubuntu/
## didn't work /etc/netplan/* sudo netplan apply systemctl restart network-manager
## worked /etc/network/interfaces sudo ifdown enp0s8 sudo ifup enp0s8
Q&A
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
