[CentOS] iptables

[Tomas Ruprich]

Wed, Sep 16, 2009 ve 03:31:43PM +0800, CentOS List napsal:
> <snip>
> 
> > *nat   # Manipulate nat table
> >
> > :PREROUTING ACCEPT [0:0]
> > :POSTROUTING ACCEPT [0:0]
> > :OUTPUT ACCEPT [0:0]
> > -A PREROUTING -t nat -p tcp --dport 26 -j REDIRECT --to-port 25
> >
> > COMMIT
> 
> Thanks Christopher,
> 
> I had updated my rules to
> 
> *nat
> :OUTPUT ACCEPT [0:0]
> :PREROUTING ACCEPT [0:0]
> :POSTROUTING ACCEPT [0:0]
> -A PREROUTING -t nat -p tcp --dport 26 -j REDIRECT --to-port 25
> COMMIT
> # Completed
> 
> When I did a restart, there is an error.
> 
> Flushing firewall rules:                                   [  OK  ]
> Setting chains to policy ACCEPT: nat mangle filter         [  OK  ]
> Unloading iptables modules:                                [  OK  ]
> Applying iptables firewall rules: iptables-restore v1.3.5: Line 52 seems to
> have a -t table option.
> 
> Error occurred at line: 52
> Try `iptables-restore -h' or 'iptables-restore --help' for more information.
>                                                            [FAILED]
> 
> Line 52 is -A PREROUTING -t nat -p tcp --dport 26 -j REDIRECT --to-port 25
> 
> Regards
> 

Never (if you aren't guru) edit your iptables by directly editing your
config. Always use iptables binary.

It is said there... -t option shouldn't be on that line. The line should 
be only 
-A PREROUTING -p tcp --dport 26 -j REDIRECT --to-port 25
because you're already in the *nat section of the config.

But again, you should enter this command instead of editing the config:
iptables -A PREROUTING -t nat -p tcp --dport 26 -j REDIRECT --to-port 25

regards
Tomas