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Firewall, NAT, Router... something is blocking me

Posted on 2003-03-19
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Last Modified: 2013-11-16
Hi,

I have a litlle problem when I want to NAT a webserver,

Current configuration :

Webserver with <web public IP> gateway : <public IP of my Firewall>  ==> everything's working fine, but unprotected.

New configuration :

Webserver with <192.168.*.*> NAT to <web public IP> gateway <private IP of DMZ> : nothing's going in nor out

OR

Webserver with <192.168.*.*> NAT to <another public IP of our range> gateway <private IP of DMZ> : everything's working perfect !


Problem :

I can't change my DNS to point to new public IP because of same problem on ftp server that is configured on all the workshops of my company. Changing DNS is not a solution !

Where can that be bloacked then ???

Please help :-)

Tess
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Question by:Tessai
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4 Comments
 
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Expert Comment

by:PaulBobby
ID: 8167905
Ok need to clear things up a little first. An ASCII diagram, or better worded description of the environment you would LIKE to implement would be much appreciated.

Also if you could specifiy products being used.
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Author Comment

by:Tessai
ID: 8168186
Sure,

I have a firewall, a LAN and a DMZ

In my LAN, I have all the workstations of my LAN working fine,
In my DMZ I have nothing up to now, exept a PCtest with FTP and WWW running on it and accessible from the internet, so the DMZ is working fine,

On my firewall, a FW1 Checkpoint, 3 NIC's, 1 for my LAN, 1 for my DMZ and 1 connected to a switch, a RJ45 goes to my cisco routeur.

Internet == router == switch ==> FW1 and up to now webserver, ftpserver, mailserver

What I would like to do is :

Internet == router == switch == FW1
FW1 linked to LAN and DMZ

What I did :

Set webserver with public IP (ie. 81.70.70.70) to private IP behind DMZ (ie 192.168.1.*), so the webserver has now 192.168.1.* and NAT to it's prior public IP. ==> not working

If I set the webserver on another public IP (ie. 81.70.70.71), it's working fine...

Why ??

Hope it's well explained....
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Accepted Solution

by:
karrik earned 500 total points
ID: 8171990
I had a similar problem last year and it turned out that a Cisco router "remembered" that the old MAC address belonged to the public IP and it never allowed the new NAT:ted MAC address for the service.

Power cycling the Cisco after I NAT:ted the server solved my problem.

You can easily see if this is the case by running tcpdump or a similar program on your setup.
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Author Comment

by:Tessai
ID: 8173443
YEAH !!! That was it !!!!


Thanks for your help !
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