Debian Setup als Router

eth0 = WAN / eth1 = LAN

1. Berarbeiten und festlegen der Netzkonfig in der interfaces Datei:

   # vim /etc/network/interfaces

2. Festlegen der fixen Angaben zum interen LAN Netzwerk:

   /etc/network/interfaces

   # This file describes the network interfaces available on your system
   # and how to activate them. For more information, see interfaces(5).
    
   source /etc/network/interfaces.d/*
    
   # The loopback network interface
   auto lo
   iface lo inet loopback
    
   # The primary network interface
   auto eth0
   iface eth0 inet dhcp
   # This is an autoconfigured IPv6 interface
   #iface eth0 inet6 auto
   auto eth1
   iface eth1 inet static
   address 172.168.1.1
   netmask 255.255.255.0
   dns-nameservers 172.168.1.1
   gateway 172.168.1.1

3. Now edit /etc/sysctl.conf and uncomment:

   # net.ipv4.ip_forward=1>

   so that it reads: net.ipv4.ip_forward=1

   and save it by entering

   :wq

4. To enable IP masquerading, enter following set of commands in terminal:

   # iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
   # iptables -A FORWARD -i eth1 -o eth0 -m state --state RELATED,ESTABLISHED -j ACCEPT
   # iptables -A FORWARD -i eth1 -o eth0 -j ACCEPT
   
   # apt‐get install iptables‐persistent
   # iptables-save > /etc/iptables/rules.v4

5. Reboot des Systems: → init 0

https://askubuntu.com/questions/590920/ubuntu-14-04-as-a-gateway-router-and-a-firewall

Bessere Lösung → https://gridscale.io/community/knowledgebase/tutorial-debian-routergateway-in-10-minuten/

Tutorial_ Debian Router_Gateway in 10 Minuten einrichten