Iptables Failover

Ziel

[Bearbeiten]

• Eine Firewall hat zwei Internetleitungen
• Eine Hauptleitung 1.1.1.1
• Eine Nebenleitung 2.2.2.2
• Falls die Hauptleitung ausfällt sollen alle Pakete (Pings, Webanfragen, VPNs) automatisch über die Nebenleitung laufen.
• VPN:
  • IP: 3.3.3.3
  • Lokales Netz: 10.0.10.0/24

Netzwerkkonfiguration

1. This file describes the network interfaces available on your system
2. and how to activate them. For more information, see interfaces(5).

source /etc/network/interfaces.d/*

1. The loopback network interface

auto lo iface lo inet loopback

1. The primary network interface

auto ens18 iface ens18 inet static

address 10.81.240.3/21
gateway 10.81.240.1

auto ens19 iface ens19 inet static

address 10.81.96.2/19
post-up ip rule add  fwmark 200 table 200
post-up ip rule add from 10.81.96.2  table 200
pre-down ip rule del  fwmark 200 table 200
pre-down ip rule del from 10.81.96.2  table 200
post-up ip route add default via 10.81.96.1 table 200

auto ens20 iface ens20 inet static

address 10.81.11.1/19
dns-nameservers 10.81.0.2

Firewall

Variablen

• vi /usr/local/etc/firewall.cfg

VODDEV=ens18
TELDEV=ens19
TELIP="10.81.96.2"
VODIP="10.81.240.3"
LANDEV=ens20
LAN="10.81.0.0/19"
LANIP="10.81.11.1"

Regeln

• vi /usr/local/sbin/firewall

#!/bin/bash
#Einlesen der Konfigurationsdatei
source /usr/local/etc/firewall.cfg
echo normal > /tmp/fw.status
case $1 in
start)
    echo "starte firewall"
    #Löschen aller Reglen
        iptables -F
        iptables -F -t nat
        iptables -F -t mangle
      
        iptables -X
        iptables -X -t nat
        iptables -X -t mangle
     
        #Setzen der Default Policy auf DROP
        iptables -P INPUT DROP
        iptables -P OUTPUT DROP
        iptables -P FORWARD DROP
        #Aktivieren des Connection Tracking Konzeptes
        iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
        iptables -A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT
        iptables -A OUTPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
        #Verkehr von Rechner hinaus freischalten
        iptables -A OUTPUT -m state --state NEW -j ACCEPT
        #Verkehr über das loopback device freischalten
        iptables -A INPUT -i lo -m state --state NEW -j ACCEPT
        #Verkehr zum Rechner ZUM TCP PORT 22 erlauben
        iptables -A INPUT -p tcp --dport 22 -m state --state NEW -j ACCEPT
        #ICMP echo-request freigeschaltet
        iptables -A INPUT -p icmp --icmp-type echo-request -m state --state NEW -j ACCEPT
     
        iptables -A FORWARD -m state --state NEW -j ACCEPT
     
        iptables -t mangle -N tel
        iptables -t mangle -A tel -j MARK --set-mark 200
     
        if test  "$2" = "backup" 
        then
    
    echo backup > /tmp/fw.status
            iptables -A PREROUTING -t mangle -s $LAN ! -d  $LAN  -j tel
            iptables -A OUTPUT     -t mangle -s $LANIP ! -d $LAN  -j tel
        fi
     
        iptables -t nat -A POSTROUTING -j SNAT -s $LAN -d 10.0.10.0/24 -o $TELDEV --to-source 172.30.28.2  
        iptables -t nat -A POSTROUTING -j SNAT  -s $LAN -o $TELDEV --to-source $TELIP
        iptables -t nat -A POSTROUTING -j SNAT -s $LAN -d 10.0.10.0/24 -o $VODDEV --to-source 172.30.28.1
        iptables -t nat -A POSTROUTING -j SNAT  -s $LAN -o $VODDEV --to-source $VODIP
     
     
        iptables -A INPUT  -j LOG  --log-prefix "--iptables-drop-in--"
        iptables -A OUTPUT -j LOG  --log-prefix "--iptables-drop-out--"
        iptables -A FORWARD -j LOG --log-prefix "--iptables-drop-for--"
;;
stop)
    echo "stoppe firewall"
    #Löschen aller Reglen
        iptables -F
        iptables -F -t nat
        iptables -F -t mangle
        iptables -X
        iptables -X -t nat
        iptables -X -t mangle
        #Setzen der Default Policy auf ACCEPT
        iptables -P INPUT ACCEPT
        iptables -P OUTPUT ACCEPT
        iptables -P FORWARD ACCEPT
;;
*)
    echo "usage: $0 start|stop"
;;
esac