Network, Basic tooling examples

# get the ip of a well knwon site
dig wikipedia.org
net=91.198.174.0
target_ip=91.198.174.192

# create a custom routing table to blackhole packets
ip route add blackhole "$net"/24 table 66
# create a rule using that routing table 66
ip rule add to "$net"/24 table 66
# check it worked
curl "http://$target_ip"
# restore to normal state
ip rule del to "$net"/24 table 66
ip route flush table 66

old_ip=192.168.1.101
new_ip=192.168.1.102
net=91.198.174.0
target_ip=91.198.174.192

# add another address to your interface
ip addr add "$new_ip"/24 dev "$dev"
# append a rule to the nat table changing the source ip
iptables -t nat -A POSTROUTING -d "$net"/24 -j SNAT --to-source "$new_ip"
# connect to $target_ip binding source address to $old_ip
netcat -s "$old_ip" "$target_ip"
# check with tcpdump the src address is $new_ip
tcpdump -nn net "$net"
# restore to normal state
iptables -t nat -F
ip addr del "$new_ip"/24 dev "$dev"

lsof -i -U -nP
# -i list ipv4 and ipv6 sockets
# -U list unix sockets
# -nP do not resolve IP addresses nor port numbers

netstat -x64 -anp
# -x64 list unix, ipv4 and ipv6 sockets
# -a list listenning and established connections
# -n do not resolve IP addresses nor port numbers
# -p show program name and PID

ss -anp
# -a list listenning and established connections
# -n do not resolve IP addresses nor port numbers
# -p show program name and PID