head:~# route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
201.xx.xx.0     201.xx.xx.1     255.255.255.0   UG    0      0        0 eth3
201.xx.xx.0     *               255.255.255.0   U     0      0        0 eth3
localnet        head.furlan     255.255.255.0   UG    0      0        0 eth0
localnet        *               255.255.255.0   U     0      0        0 eth0
200.xx.xx.0     200.xx.xx.1    255.255.255.0    UG    0      0        0 eth1
200.xx.xx.0     *               255.255.255.0   U     0      0        0 eth1
default         200.xx.xx.1    0.0.0.0          UG    0      0        0 eth1
default         head.furlan     0.0.0.0         UG    0      0        0 eth0


head:~# cat f1r3
#!/bin/sh

LAN=eth0
LAN_CLASSE=192.168.1.0/24
LINK1=eth1
LINK2=eth3
GW1=200.xx.xx.1
GW2=201.xx.xx.1
MARK1=11
MARK2=12
T1=telefonica
T2=embratel

/etc/init.d/networking restart

echo "[Apagando regras]"
iptables -X
iptables -F
iptables -t nat -X
iptables -t nat -F
iptables -t mangle -X
iptables -t mangle -F

echo "[Ativando compartilhamento]"
ip rule add fwmark $MARK1 table $T1 prio 20
ip rule add fwmark $MARK2 table $T2 prio 20
ip route add default via $GW1 dev $LINK1
ip route append default via $GW2 dev $LINK2

route del default dev $LINK2
route del default dev $LINK2
route del default dev $LINK2
route del default dev $LINK2
route del default dev $LINK2
route del default dev $LINK2
route del default dev $LINK2
route del default dev $LINK2
route del default dev $LINK2
route del default dev $LINK2
route del default dev $LINK2
route del default dev $LINK2
route del default dev $LINK2
route del default dev $LINK2
route del default dev $LINK2
route del default dev $LINK2
route del default dev $LINK2
route del default dev $LINK2
route del default dev $LINK2
route del default dev $LINK2
route del default dev $LINK2
route del default dev $LINK2
route del default dev $LINK2
route del default dev $LINK2

ip route flush cache

iptables -A INPUT -p tcp --syn -s 192.168.1.0/255.255.255.0 -j ACCEPT

iptables -A POSTROUTING -t nat -s $LAN_CLASSE -o $LINK1 -j MASQUERADE
iptables -A POSTROUTING -t nat -s $LAN_CLASSE -o $LINK2 -j MASQUERADE