Several application scenarios of NAT

1、 Let other network ports in the same device access the Internet

The functions of the following figure , It's really just a 4G Router , You can connect to the Internet by cable , You can also access the Internet wirelessly .

Can pass NAT Rules are easily implemented .

  such as ,LTE Module dialing succeeded , The name of the network port is   lte0

in the light of wifi ap :

service isc-dhcp-server stop
sed "/INTERFACES=/c\INTERFACES=wlan0" -i /etc/default/isc-dhcp-server
sed "/interface=/c\interface=wlan0" -i /etc/hostapd/hostapd.conf

hostapd -B /etc/hostapd/hostapd.conf
sleep 1

ifconfig wlan0 10.5.5.1/24
service isc-dhcp-server restart

echo "1" > /proc/sys/net/ipv4/ip_forward
iptables -t nat -A POSTROUTING -o lte0 -j MASQUERADE

iptable perform Masquerade, Source IP Change to host network card IP, Then send the request to the Internet server .

The principle is as follows ：

 

 

$ cat /etc/default/isc-dhcp-server
# Defaults for isc-dhcp-server initscript
# sourced by /etc/init.d/isc-dhcp-server
# installed at /etc/default/isc-dhcp-server by the maintainer scripts

#
# This is a POSIX shell fragment
#

# Path to dhcpd's config file (default: /etc/dhcp/dhcpd.conf).
#DHCPD_CONF=/etc/dhcp/dhcpd.conf

# Path to dhcpd's PID file (default: /var/run/dhcpd.pid).
#DHCPD_PID=/var/run/dhcpd.pid

# Additional options to start dhcpd with.
#       Don't use options -cf or -pf here; use DHCPD_CONF/ DHCPD_PID instead
#OPTIONS=""

# On what interfaces should the DHCP server (dhcpd) serve DHCP requests?
#       Separate multiple interfaces with spaces, e.g. "eth0 eth1".
INTERFACES="wlp1s0"



$ cat /etc/hostapd/hostapd.conf 
interface=wlP2p1s0
driver=nl80211
ssid=test
channel=6
hw_mode=g
auth_algs=1
wpa=3
wpa_passphrase=12345678
wpa_key_mgmt=WPA-PSK
wpa_pairwise=TKIP
rsn_pairwise=CCMP