CentOS - Jun 2007 - OT - IP Tables - forwarding to localhost

Hi,

I am trying to set up a firewall rule so calls to old_mailserver:25 get
redirected to localhost:25. I have seen quite a few rules and none seem
to work.

I have tried with the firewall enabled (configured to allow smtp) and
disabled, but it doesn't seem to make a difference.

One of the commands I have been using is:
/sbin/iptables -t nat -I PREROUTING -p tcp -d old_mailserver_ip/32
--dport 25 -j REDIRECT --to 127.0.0.1:25

Am I missing anything?

Thanks

Gabriel


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Hi,

Try this:

iptables -t nat -A PREROUTING -p tcp -d old_mailserver_ip 
--destination-port 25 -j DNAT --to-destination 127.0.0.1:25

first last wrote:
> Hi,
>
> I am trying to set up a firewall rule so calls to old_mailserver:25 get
> redirected to localhost:25. I have seen quite a few rules and none seem
> to work.
>
> I have tried with the firewall enabled (configured to allow smtp) and
> disabled, but it doesn't seem to make a difference.
>
> One of the commands I have been using is:
> /sbin/iptables -t nat -I PREROUTING -p tcp -d old_mailserver_ip/32
> --dport 25 -j REDIRECT --to 127.0.0.1:25
>
> Am I missing anything?
>
> Thanks
>
> Gabriel
>
>
>       ___________________________________________________________ 
> Yahoo! Mail is the world's favourite email. Don't settle for less,
sign up for
> your free account today
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> CentOS at centos.org
> http://lists.centos.org/mailman/listinfo/centos
>

On Mon, Jun 18, 2007 at 11:46:42AM +0100, first last
wrote:
> Hi,
> 
> I am trying to set up a firewall rule so calls to old_mailserver:25 get
> redirected to localhost:25. I have seen quite a few rules and none seem
> to work.
> 
> I have tried with the firewall enabled (configured to allow smtp) and
> disabled, but it doesn't seem to make a difference.
> 
> One of the commands I have been using is:
> /sbin/iptables -t nat -I PREROUTING -p tcp -d old_mailserver_ip/32
> --dport 25 -j REDIRECT --to 127.0.0.1:25
Try this:
iptables -t nat -I PREROUTING -p tcp -d old_mail_server_ip --dport 25 \
  -j REDIRECT
iptables -t nat -I OUTPUT -p tcp -d old_mail_server_ip --dport 25 \
  -j REDIRECT
 
> Am I missing anything?
Locally generated packets go through OUTPUT, but not PREROUTING, IIRC.

-- 
lfr
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--- Luciano Rocha <strange at nsk.no-ip.org> wrote:
> On Mon, Jun 18, 2007 at 11:46:42AM +0100, first last wrote:
> > Hi,
> > 
> > I am trying to set up a firewall rule so calls to old_mailserver:25
> get
> > redirected to localhost:25. I have seen quite a few rules and none
> seem
> > to work.
> > 
> > I have tried with the firewall enabled (configured to allow smtp)
> and
> > disabled, but it doesn't seem to make a difference.
> > 
> > One of the commands I have been using is:
> > /sbin/iptables -t nat -I PREROUTING -p tcp -d old_mailserver_ip/32
> > --dport 25 -j REDIRECT --to 127.0.0.1:25
> 
> Try this:
> iptables -t nat -I PREROUTING -p tcp -d old_mail_server_ip --dport 25
> \
>   -j REDIRECT
> iptables -t nat -I OUTPUT -p tcp -d old_mail_server_ip --dport 25 \
>   -j REDIRECT
Thanks, this worked! This just saved me a reboot on the production
servers :)

Thanks to all who responded.

Gabriel 


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