Connect ubuntu machine directly

1 Machine A

$iwconfig to find inet interface name enp1s0 or eno1

2 sudo vi /etc/network/interfaces

iface enp1s0 inet static

address 192.168.1.250

gateway 192.168.1.250

netmask 255.255.255.0

3 sudo ifdown enp1s0;sudo ifup enp1s0

4 $ifconfig to see the result

5 Machine B

sudo vi /etc/network/interfaces

iface enp1s0 inet static

address 192.168.1.251

gateway 192.168.1.250

netmask 255.255.255.0

nameserver 8.8.8.8

then ifdown,ifup,ifconfig

Now Machine B can ping Machine A

6 Config NAT on machine A

sudo echo 1 > /proc/sys/net/ipv4/ip_forward

sudo iptables -F

sudo iptables -P INPUT ACCEPT 

sudo iptables -P FORWARD ACCEPT

sudo  iptables -t nat -A POSTROUTING -o wlp2s0 -j MASQUERADE (wlp2s0 ： wifi iface)

Now Machine B can ping any address

7 Error when ping: Name or service not known

vi /etc/resolv.conf add nameserver 8.8.8.8

(optional) /etc/hosts add Machine B' name: 192.168.1.251 xxxx

(optional) edit /etc/sysconfig/network

NETWORKING=yes

HOSTNAME=xxxx

**** After Machine B reboot, sudo ifup eno1 is reqiured (not ifdown).