I have a problem with mi linux BOX
.
Eth0 =  192.168.0.254  (RED A)
Eth1 =  200.69.123.177/130  (LINK A)
Eth2 =  192.168.0.100  (RED B)
Eth3 =  192.168.1.1 para el PPPOE 
ppp0=  DynamicIP (LINK B)
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DEFAULT ROUTE
200.69.123.178 (LINKA)
ppp0 (cdo establece el PPPOE)
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IPTABLES  NAT RULES
iptables -t nat -A POSTROUTING -s 192.168.0.0/255.255.255.128 -o ppp0 -j MASQUERADE
iptables -t nat -A POSTROUTING -s 192.168.0.128/255.255.255.128 -o eth1 -j MASQUERADE
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My problem is the only NAT works is the NAT with march with de default route..
 
Can any one helme?