Adrián Bíro

Networing Notes

Basic Network Troubleshooting

ip

ip-route

To avoid a non-deterministic lag between the time that a new route is entered into the kernel routing tables and the time that a new lookup in those route tables is performed, use on Linux kernel version < 3.6 routing cache

$ ip route flush cache
$ ip route get 10.0.1.138
10.0.1.138 dev wlp0s20f3 src 10.0.1.21 uid 1000 
    cache

Show Interface

ip addr | awk -F':' '/^[1-9]/{$2=$2; print $2}'
ip link show
netstat -i
nmcli connection show

tcpdump

Tcpdump tutorial

trafic on wifi interface UDP

sudo tcpdump -i $(ip addr | awk -F':' '/^[1-9]/{print $2}'| grep wlp) udp -v

ssh trafic

sudo tcpdump 'tcp port 22' -l -e
sudo tcpdump -n ip and udp and port 53

ss

ss -4
sudo ss -tnlp