Port forwarding from IPCop to Cisco PIX Firewall

Unanswered Question
Jan 30th, 2010

Hi All,

I am attempting to forward port 80 and port 25 from an IPCop FW connected to Internet via the ADSL router port and my Cisco FW connected in the protected area (Green Zone) of my LAN. A similar diagram of my network is depicted in the Cisco link https://www.cisco.com/en/US/tech/tk648/tk361/technologies_tech_note09186a0080093f31.shtml. The only differences are the TCP-IP addresses and the Outside Cloud which is Internet in my case.

I would greatly appreciate an hint or a clue which helps me to fix this issue I have.

Data which may better help you to understand the environment, if you can assist.

Cisco PIX Firewall Version 6.3(3)
Cisco PIX Device Manager Version 3.0(1)  -------> works well if directly connected to the ADSL Router and to Internet. Everything works. Good configuration available in the attachement.

IPCop 1.4.2  ------> works well if directly connected to the ADSL Router and to Internet. I can HTTP from Internet to an a Web Server directly connected to its internat Interface. I.e.

  • Cisco PIX FW alllows all services from the internal network to reach Internet, via the IPCop Green (Internal interface);
  • Traffic like Facebook, Skype, etc. is allowed from/to Internet to my protected zone and vice-versa;
  • Cisco internal network is 194.20.23.X is privately assigned to an other company and used by chance but without problems for years;
  • Cisco external network I/F is It connects to the internal IPCop interface (Green);
  • IPCop external network I/F is, which connects to my ADSL Router GW

What exactly doesn't work:

My SMTP, DNS and MAIL server public address is If you ping to this address it responds. However, if you try to telnet to port 25, it doesn't respond. So, I am almost sure there is a rule which prevents the port forwarding to my server, which Cisco NAT translates to


A working configuration when Cisco is directly connected to Internet;

A non working configuration when Cisco is not directly connected to Internet.  (File Cisco_Config_3001.txt)




I have this problem too.
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sokakkar Mon, 02/15/2010 - 07:28


I believe this is the set up which is not working:>(>( Cop(>( ADSL router-->Internet

Following is relevant configuration on PIX:

name linux

name mailgate

ip address outside

ip address inside

access-list outside permit tcp any host mailgate eq smtp log

access-list outside permit tcp any host mailgate eq www log

static (inside,outside) tcp mailgate www linux www netmask 0 0

static (inside,outside) tcp mailgate smtp linux smtp netmask 0 0

route outside mailgate 1

route inside linux 1

route outside 1

Since we have a static nat translation for linux with mailgate on PIX, i believe IP Cop is not doing the translation for mailgate IP but since 82.70.219.x subnet is directly connected to IP Cop it will never forward the traffic for to PIX as directly connected network takes precedence over static routes.

Here is an option to get this working with this setup:

Translation on IP Cop:> free IP of this range)

On PIX translation:>


static (inside,outside) tcp smtp smtp netmask

static (inside,outside) tcp http http netmask

access-list outside permit tcp any host eq smtp log

access-list outside permit tcp any host eq www log

I hope this helps.

Warm Regards,

Sourav Kakkar

[email protected]


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