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Linux NAT with 3g PPP connection

Shell Script (Bash) posted 7 months ago by marko

I run this nat.sh script whenever I need to share my 3g connection to other computers in the switch I’m plugged into. Please note that it resets existing iptables rules. 

   1  #!/bin/bash
   2  iptables --flush            
   3  iptables --table nat --flush
   4  iptables --delete-chain
   5  iptables --table nat --delete-chain
   6  
   7  echo 1 > /proc/sys/net/ipv4/ip_forward
   8  
   9  internal=eth0
  10  external=ppp0
  11  /sbin/iptables -t nat -A POSTROUTING -o ${external} -j MASQUERADE
  12  /sbin/iptables -A FORWARD -i ${external} -o ${internal} -m state --state RELATED,ESTABLISHED -j ACCEPT
  13  /sbin/iptables -A FORWARD -i ${internal} -o ${external} -j ACCEPT

Tagged nat, linux, iptables