Problemas con nat

[Jose Miguel Vidal Lavin]

Señores

	Tengo una máquina que funciona com squid proxy y funciona bien, 
inclusive me filtra msn, kazaa y demases. El problema es que tengo ke 
usar nat para habilitar todos los servicios a ciertas máquinas y eso lo 
hago desde una máquina que tengo de firewall pero de un momento a otro 
dejó de funcionar el ruteo y no me puedo conectar a internet usando esa 
puerta de enlace, he revisado toda la configuración y no he podido 
encontrar el error.

	mi configuración que me entrega iptables es la siguiente:

Tabla: mangle
Chain PREROUTING (policy ACCEPT)
target     prot opt source               destination

Chain INPUT (policy ACCEPT)
target     prot opt source               destination

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination

Chain POSTROUTING (policy ACCEPT)
target     prot opt source               destination
Tabla: filter
Chain INPUT (policy DROP)
target     prot opt source               destination
ACCEPT     icmp --  anywhere             anywhere           icmp 
echo-request
ACCEPT     tcp  --  anywhere             anywhere           tcp dpt:ssh
ACCEPT     tcp  --  anywhere             anywhere           tcp spt:ssh
ACCEPT     tcp  --  anywhere             anywhere           tcp dpt:ftp
ACCEPT     tcp  --  anywhere             anywhere           tcp dpt:ftp-data
ACCEPT     tcp  --  anywhere             anywhere           tcp dpt:http
ACCEPT     tcp  --  anywhere             anywhere           tcp spt:http
ACCEPT     tcp  --  anywhere             anywhere           tcp dpt:smtp
ACCEPT     tcp  --  anywhere             anywhere           tcp spt:smtp
ACCEPT     tcp  --  anywhere             anywhere           tcp dpt:pop3
ACCEPT     tcp  --  anywhere             anywhere           tcp spt:pop3
ACCEPT     udp  --  anywhere             anywhere           udp 
dpt:netbios-ns
ACCEPT     tcp  --  anywhere             anywhere           tcp 
dpt:netbios-ssn
ACCEPT     tcp  --  anywhere             anywhere           tcp 
dpt:microsoft-ds
ACCEPT     udp  --  anywhere             anywhere           udp 
spt:netbios-ns
ACCEPT     tcp  --  anywhere             anywhere           tcp 
spt:netbios-ssn
ACCEPT     tcp  --  anywhere             anywhere           tcp 
spt:microsoft-ds
REJECT     tcp  --  anywhere             anywhere           tcp 
dpt:sunrpc reject-with icmp-port-unreachable

Chain FORWARD (policy DROP)
target     prot opt source               destination
ACCEPT     tcp  --  anywhere             anywhere           tcp dpt:http
ACCEPT     tcp  --  anywhere             anywhere           tcp spt:http
ACCEPT     udp  --  anywhere             anywhere           udp dpt:http
ACCEPT     udp  --  anywhere             anywhere           udp spt:http

Chain OUTPUT (policy DROP)
target     prot opt source               destination
ACCEPT     icmp --  anywhere             anywhere           icmp echo-reply
ACCEPT     icmp --  anywhere             anywhere
ACCEPT     tcp  --  anywhere             anywhere           tcp dpt:ssh
ACCEPT     tcp  --  anywhere             anywhere           tcp spt:ssh
ACCEPT     tcp  --  anywhere             anywhere           tcp spt:ftp
ACCEPT     tcp  --  anywhere             anywhere           tcp spt:ftp-data
ACCEPT     tcp  --  anywhere             anywhere           tcp dpt:domain
ACCEPT     udp  --  anywhere             anywhere           udp dpt:domain
ACCEPT     tcp  --  anywhere             anywhere           tcp dpt:http
ACCEPT     tcp  --  anywhere             anywhere           tcp spt:http
ACCEPT     tcp  --  anywhere             anywhere           tcp spt:10000
ACCEPT     tcp  --  anywhere             anywhere           tcp dpt:smtp
ACCEPT     tcp  --  anywhere             anywhere           tcp spt:smtp
ACCEPT     tcp  --  anywhere             anywhere           tcp dpt:pop3
ACCEPT     tcp  --  anywhere             anywhere           tcp spt:pop3
ACCEPT     udp  --  anywhere             anywhere           udp 
dpt:netbios-ns
ACCEPT     tcp  --  anywhere             anywhere           tcp 
dpt:netbios-ssn
ACCEPT     tcp  --  anywhere             anywhere           tcp 
dpt:microsoft-ds
ACCEPT     udp  --  anywhere             anywhere           udp 
spt:netbios-ns
ACCEPT     tcp  --  anywhere             anywhere           tcp 
spt:netbios-ssn
ACCEPT     tcp  --  anywhere             anywhere           tcp 
spt:microsoft-ds
Tabla: nat
Chain PREROUTING (policy ACCEPT)
target     prot opt source               destination

Chain POSTROUTING (policy ACCEPT)
target     prot opt source               destination
MASQUERADE  all  --  anywhere             anywhere

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination

-- 
Jose Miguel Vidal Lavin       User #333809 http://couter.li.org
Departamento de Informática                      Fono : 6764600
Cobranzas y Servicios Afines                            6764622
Bulnes 317, Oficina 612