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DNAT

DISCUSSION Payal Rathod 3 participants 3 messages Oct 26, 2004

lore
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#0 lore raw

Hi,
I want to access my internal machine from outside. But I am unable to do so. I tried,

# iptables -t nat -I PREROUTING -d <my_ext_ip> -p tcp --dport
8081 -j DNAT --to-destination 192.168.0.16:80
# iptables -I INPUT -p tcp --dport 8081 -j ACCEPT
# iptables -I FORWARD -s 192.168.0.16 -j ACCEPT

I know these are very crude but they are simple to start with. Also, once I get one more public IP from my ISP, I will NAT it to the internal machine.
Can anyone give pointers on this and above to why it is not working? If this is right, is it possible that my ISP might be blocking traffic from outside to ports other than the few.

With warm regards,
-Payal

#1 lore raw
Quoted 7 lines · Payal Rathod

Hi,
I want to access my internal machine from outside. But I am unable to do so. I tried,

# iptables -t nat -I PREROUTING -d <my_ext_ip> -p tcp --dport
8081 -j DNAT --to-destination 192.168.0.16:80
# iptables -I INPUT -p tcp --dport 8081 -j ACCEPT

the one above is useless because the INPUT chain in this case is not traversed.

Quoted 3 lines
# iptables -I FORWARD -s 192.168.0.16 -j ACCEPT

This one is the one u need ... but u have to make the check on destination and not on source so #iptables -I FORWARD -d 192.168.0.16 -j ACCEPT

Quoted 5 lines

With warm regards,
-Payal

bye :)

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#2 lore raw
In reply to Payal Rathod
Quoted 5 lines · Payal Rathod

Hi,
I want to access my internal machine from outside. But I am unable to do so. I tried,

# iptables -t nat -I PREROUTING -d <my_ext_ip> -p tcp --dport
8081 -j DNAT --to-destination 192.168.0.16:80

that looks ok...keep in mind you'll need to go to:
http://<my_ext_ip>:8081 to hit the server from the outside

Quoted 1 line
# iptables -I INPUT -p tcp --dport 8081 -j ACCEPT

nope--try:

  iptables -A FORWARD -p tcp -d 192.168.0.16 --dport 80 -j ACCEPT

once PREROUTING is traversed--the packet is forever changed from the perspective of all remaining chains.

Quoted 1 line
# iptables -I FORWARD -s 192.168.0.16 -j ACCEPT

i guess the point of that is to allow the replies back? ok, i guess...

-j

Signature · 1 line
Jason Opperisano <[email protected]>