Networking¶

Configuration¶

ifconfig¶

ip addr
ip addr show
ifconfig
ifconfig -a
ifdown enp0s3
ifup enp0s3
ifconfig enp0s3 192.168.0.150/24 # Not Permanent

Add Secondary IP¶

Link

ifconfig eth0:1 172.31.81.196 netmask 255.255.240.0 up # Not Permanent

Remove Secondary Ip¶

ip addr del 172.31.81.196/20 dev eth0:1 # Not Permanent

Network-Manager¶

sudo apt install network-manager
sudo service network-manager restart
nmcli
nmcli connection # Connection information
# Add Static Route
sudo nmcli connection add con-name STATIC ipv4.addresses 192.168.58.1/24 ifname eth0 type ethernet
nmcli connection show STATIC
sudo nmcli connection modify  STATIC +ipv4.routes "172.16.0.0/16 192.168.58.254" ipv4.dns 172.16.58.254

Routes¶

route
route -n
route add default gw 192.168.0.254

Dns¶

cat /etc/hosts
cat /etc/nsswitch.conf # show how priority to will resolve dns

cat /etc/resolv.conf
cat /etc/dhcp/dhclient.conf

sudo service networking restart

File¶

cat /etc/network/interfaces

IP Tables¶

Nat

sudo iptables -t nat -L | grep 100.66.20.131

sudo iptables -t nat -L | grep nginx-service

Troubleshooting¶

Netstat¶

$ sudo netstat -nl -p tcp  | grep 8123
$ sudo netstat -nl -p tcp  | head

Get open ports¶

nmap localhost
netstat -at

SS¶

ss -an | grep -i listen

sudo ss -ntlp # To get process

Who listen on Port¶

sudo lsof -i :8000

Test Remote Connection to port¶

nc -v 10.240.100.18  2049

netcat -l 12345 # To listen a Port

Get Ports than services are listen¶

cat /etc/services

MTR¶

mtr acloud.com

DNS¶

host google.com
dig google.com

TCP Dump¶

sudo tcpdump -v -l -i any 'host 100.65.17.226'

tcpdump -n port 6443

tcpdump port 443 and '(tcp-syn|tcp-ack)!=0'

VPN¶

Permanent VPN Connection¶

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