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¿Por qué no puedo agregar ninguna regla de iptables?

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¿Por qué no puedo agregar ninguna regla de iptables?

¿Por qué no puedo agregar ninguna regla de iptables?

root@ROUTER:~# iptables -L INPUT -v
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
6934 685K ACCEPT 0 -- any any anywhere anywhere state RELATED,ESTABLISHED
0 0 DROP udp -- ppp0 any anywhere anywhere udp dpt:route
0 0 DROP udp -- br0 any anywhere anywhere udp dpt:route
0 0 ACCEPT udp -- any any anywhere anywhere udp dpt:route
2 120 logaccept tcp -- any any anywhere ROUTER tcp dpt:22
0 0 DROP icmp -- ppp0 any anywhere anywhere
0 0 DROP igmp -- any any anywhere anywhere
5 350 ACCEPT 0 -- lo any anywhere anywhere state NEW
568 35947 logaccept 0 -- br0 any anywhere anywhere state NEW
339 38020 DROP 0 -- any any anywhere anywhere

Luego trato de agregar una regla:

root@ROUTER:~# /usr/sbin/iptables -I INPUT -i ppp0 -m multiport --dport 21,22,23,53,67,80,443 -j DROP

Pero no se agregó a la lista:

root@ROUTER:~# iptables -L INPUT -v
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
6992 690K ACCEPT 0 -- any any anywhere anywhere state RELATED,ESTABLISHED
0 0 DROP udp -- ppp0 any anywhere anywhere udp dpt:route
0 0 DROP udp -- br0 any anywhere anywhere udp dpt:route
0 0 ACCEPT udp -- any any anywhere anywhere udp dpt:route
2 120 logaccept tcp -- any any anywhere ROUTER tcp dpt:22
0 0 DROP icmp -- ppp0 any anywhere anywhere
0 0 DROP igmp -- any any anywhere anywhere
5 350 ACCEPT 0 -- lo any anywhere anywhere state NEW
569 36007 logaccept 0 -- br0 any anywhere anywhere state NEW
343 38428 DROP 0 -- any any anywhere anywhere

Intento agregar una regla nuevamente:

root@ROUTER:~# /usr/sbin/iptables -I INPUT -i ppp0 --dport 21 -j DROP

Y vea si hay algún cambio:

root@ROUTER:~# iptables -L INPUT -v
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
7142 704K ACCEPT 0 -- any any anywhere anywhere state RELATED,ESTABLISHED
0 0 DROP udp -- ppp0 any anywhere anywhere udp dpt:route
0 0 DROP udp -- br0 any anywhere anywhere udp dpt:route
0 0 ACCEPT udp -- any any anywhere anywhere udp dpt:route
2 120 logaccept tcp -- any any anywhere ROUTER tcp dpt:22
0 0 DROP icmp -- ppp0 any anywhere anywhere
0 0 DROP igmp -- any any anywhere anywhere
5 350 ACCEPT 0 -- lo any anywhere anywhere state NEW
574 36309 logaccept 0 -- br0 any anywhere anywhere state NEW
346 38780 DROP 0 -- any any anywhere anywhere

Pero no lo hay.. :D

Información de versión:

root@ROUTER:~# iptables -V
iptables v1.3.7

¿POR QUÉ?

Firmware: DD-WRT v24-sp2 (07/08/10) estándar

Respuesta1

iptables -I INPUT -i ppp0 --dport 21 -j DROPes sintácticamente incorrecto (carece de especificación de protocolo), por lo tanto podemos asumir que simplemente falla silenciosamente. Éste es correcto:

iptables -I INPUT -i ppp0 --dport 21 -j DROP -p tcp

Así que pruébalo.

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