connect to internet problem

Lord of Gore lordofgore at logsoftgrup.ro
Wed Dec 20 10:22:45 UTC 2006


tamer amr wrote:
> hi 
>  
>  i changed Chain INPUT policy tot DROP   and accept only what i need and make this in the OUTPUT chain and the FORWARD chain 
>   but when i try to connect the internet from any host in local network i can't why?
>  
>  in the FORWARD chain i accept any packet come from my local network 
>  
>  thank you in advance
>  
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>   
Internet browsing requires domain resolution and nat.
Keep in mind how packets travel through iptables and the fact that 
outgoing chain is used by packets that originate from the localhost. The 
chain traversed by packets originating from another host is FORWARD: 
http://iptables-tutorial.frozentux.net/images/tables_traverse.jpg

When you try to resolve iptables problems do the following:
0. Read man page. They didn't bother to write it unless it was intended 
for some use...
1. Add a log rule to every chain and use --log-prefix <chain_name> to 
differentiate between them. You might also want to try  --log-ip-options 
--log-tcp-options
2. Check out the logs and see what is going on
It gets really easy to see what kind of traffic is blocked while 
checking these log lines:

<logprefix> IN=eth0 OUT= MAC=<mac> SRC=<sourceip> DST=<destip> LEN=393 
TOS=0x08 PREC=0x00 TTL=41 ID=41464 PROTO=<protoused> SPT=<sourceport> 
DPT=<destport> LEN=373




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