auto lo
iface lo inet loopback

auto eth0
iface eth0 inet manual
auto eth1
iface eth1 inet manual

# Bridge interface
auto br0
iface br0 inet dhcp
      bridge_ports eth0 eth1
      bridge_hw aa:bb:cc:dd:ee:ff

# pre-set interface IP for client requirements, if DHCP is not working
auto br0:1
iface br0:1 inet static
    address 172.16.21.150
    netmask 255.255.255.0
    network 172.16.21.0
    broadcast 172.16.21.255
    # Gateway
    post-up route add default gw 172.16.21.254
    pre-down route del default gw 172.16.21.254


# Set default fallback interface IP address
auto br0:100
iface br0:100 inet static
    address 169.254.111.111
    netmask 255.255.255.0
    network 169.254.111.0
    broadcast 169.254.111.255

# IP Forwarding im Kernel aktivieren
echo 1 > /proc/sys/net/ipv4/ip_forward

# Masqerading auf br0 und br0.1 aktivieren
iptables -t nat -A POSTROUTING -o br0 -j MASQUERADE
iptables -t nat -A POSTROUTING -o br0:1 -j MASQUERADE

# Forwarding Regeln einrichten
# Forwarding etablierter Verbindungen von extern (br0 & br0.1) nach intern (br0.100)
iptables -A FORWARD -i br0 -o br0:100 -m state --state RELATED,ESTABLISHED -j ACCEPT
iptables -A FORWARD -i br0:1 -o br0:100 -m state --state RELATED,ESTABLISHED -j ACCEPT

# Forwarding aller Verbindungen von intern (br0.100) nach extern (br0 & br0.1)
iptables -A FORWARD -i br0:100 -o br0 -j ACCEPT
iptables -A FORWARD -i br0:100 -o br0:1 -j ACCEPT

iptables -t nat -A POSTROUTING -o br0 -j MASQUERADE

iptables -A FORWARD -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT
iptables -A FORWARD --src 169.254.111.112 -j ACCEPT

sysctl -w net.ipv4.conf.all.send_redirects=0