Question

Configuring nat on device behind two firewalls

Asked by: kapoor_sumeet

I have got two firewalls . One is fortigate and other is cisco pix.

Fortigate WAN interface  is connected to internet and cisco eth1 is connected to fortigate  internal interace using cross cable.

Ciso eth0 is connected to internal switch.

Now i have to make available my internal mail server to outside world. Please help me how to nat this system so that people can access it from outside world.

Regards,
Sumeet Kapoor

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Asked On
2009-06-12 at 03:16:11ID24486122
Topics

Proxy/Firewall Anti-Virus

,

Cisco PIX Firewall

Participating Experts
2
Points
500
Comments
2

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Answers

 

by: theric76Posted on 2009-06-12 at 03:36:19ID: 24610816

I will assume that both Fortigate and Cisco are already configured to use nat, so you will have to configure two nat rules:

1) Configure Fortigate appliance to enable port forwarding
http://kc.forticare.com/default.asp?id=2945&SID=&Lang=1
you must use your Cisco eth1 IP address as target (called "mapped PC")

2) Configure Cisco router to enable port forwarding with this
ip nat inside source static tcp [internal_IP] [port] [external_IP] [port] extendable

where you must replace values as follows:
internal_IP: the local IP address of your server
external_IP: IP address assigned to your eth1 interface on Cisco device
port: the port number of the service you are exposing

Hope this helps
theric

 

by: xiwanmPosted on 2009-06-15 at 21:30:35ID: 24634859

Hi Kapoor,

Please give us a few details about your setup :

Do you need to redirect all the Internet traffic to the Cisco Router ?
Do you have DMZs configured in your Fortigate ?
Did your ISP give a range of Public IPs or just one ?

You should consider to configure the Fortigate unit in transparent mode, as it stills filter Antivirus, IPS, Web Browsing, Antispam and allows IPSEC VPN.

xiwanm

20120131-EE-VQP-002

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