Centos Server & Ubuntu desktop Setting

Install&Setting

Install Ubuntu
Firewall with UFW
NAT - dhcp
V
F
N

Ubuntu Server installation

refer
https://www3.ntu.edu.sg/home/ehchua/programming/howto/UbuntuServer_HowTo.html#zz-1.1

Firewall with UFW

apt install ufw

vim /etc/default/ufw
make sure "IPV6=yes"

ufw enable
ufw allow ssh
ufw allow 22
ufw allow 6000:6007/tcp /* Specific Port Ranges */
ufw allow 6000:6007/udp

ufw status verbose   /* display inactive or active
ufw status numbered  /* get a list of your firewall rules

ufw disable
ufw reset

ufw allow from  203.0.113.4  /* Specific IP Addresses */ 
ufw allow from  203.0.113.4 to any port 22  /*allow 203.0.113.4 to connect to port 22 (SSH) */

ufw allow in on eth0 to any port 80
/*if your server has a public network interface called eth0, you could allow HTTP traffic port 80  

ufw deny from  203.0.113.4  /*deny all connections from 203.0.113.4 
ufw deny http

refer 
https://www.digitalocean.com/community/tutorials/how-to-set-up-a-firewall-with-ufw-on-ubuntu-18-04

NAT

ip addr show  /* current ip# */
dhclient -r; sudo dhclient  /* release * renew ip dhcp */

Static IP Address
vim /etc/network/interfaces.

# eth0 for the first network card with static IP address
auto eth0
iface eth0 inet static
address x.x.x.x
netmask 255.255.255.0
gateway x.x.x.x
dns-nameservers x.x.x.x x.x.x.x

ifup eth0
ifdown eth0

update network config using Netplan