Cisco PIX 500 Series Security Appliances

Configuring the PIX Firewall with Mail Server Access on Inside Network

Document ID: 8122

Updated: Sep 30, 2008



This sample configuration demonstrates how to set up the PIX Firewall for access to a mail server located on the inside network.

Note: The SMTP inspection configured in this document is not compatible with ESMTP connections to servers such as Microsoft Exchange. Do not configure SMTP inspection if you use a mail server that relies on ESMTP. Alternatively, PIX Software version 7.0 and later supports SMTP and ESMTP inspection.



There are no specific requirements for this document.

Components Used

The information in this document is based on these software and hardware versions:

  • PIX Firewall 10000

  • PIX Firewall software release 5.1(4)

The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, make sure that you understand the potential impact of any command.


Refer to the Cisco Technical Tips Conventions for more information on document conventions.


In this section, you are presented with the information to configure the features described in this document.

Note: Use the Command Lookup Tool (registered customers only) to obtain more information on the commands used in this section.

Network Diagram

This document uses this network setup.



This document uses these configurations.

PIX Firewall
PIX Version 5.1(4)

 !--- These commands name and set the security level for each PIX interface.

 nameif ethernet0 outside security0
 nameif ethernet1 inside security100
 enable password 8Ry2YjIyt7RRXU24 encrypted
 passwd 2KFQnbNIdI.2KYOU encrypted
 hostname PIX_1
 fixup protocol ftp 21
 fixup protocol http 80
 fixup protocol h323 1720
 fixup protocol rsh 514
 fixup protocol smtp 25
 fixup protocol sqlnet 1521
 no names

 !--- Create an access list that permits SMTP traffic from anywhere
 !--- to the host at (our server).  The name of this list is 
 !--- smtp. Add additional lines to this access list as required.
 !--- Note: There is one and only one access list allowed per
 !--- interface per direction (for example, inbound on the outside interface).
 !--- Because of limitation, any additional lines that need placement in
 !--- the access list need to be specified here.  If the server
 !--- in question is not SMTP, replace the occurrences of SMTP with
 !--- www, DNS, POP3, or whatever else is required. The access-list
 !--- command was introduced in PIX Software Release 5.0; it is used
 !--- here instead of a conduit statement.

 access-list smtp permit tcp any host eq smtp
 pager lines 24
 logging on
 logging timestamp
 no logging standby
 logging console debugging
 logging monitor debugging
 logging buffered debugging
 logging trap debugging
 no logging history
 logging facility 23
 logging queue 512

 !--- Set each Ethernet interface to auto-detect its media type.

 interface ethernet0 auto
 interface ethernet1 auto
 mtu outside 1500
 mtu inside 1500

 !--- Define the IP address for each interface.

 ip address inside
 ip address outside
 no failover
 arp timeout 14400

 !--- Specify that any traffic that originates inside from the
 !--- 192.168.2.x network NATs (PAT) to if
 !--- such traffic passes through the outside interface.

 global (outside) 1
 nat (inside) 1

 !--- Define a static translation between on the inside and
 !--- on the outside.  These are the addresses to be used by
 !--- the server located inside the firewall.

 static (inside,outside) netmask

 !--- Apply the access list named smtp inbound on the outside interface.

 access-group smtp in interface outside

 !--- Set the default route to 
 !--- The PIX assumes that this address is that of a router.

 route outside 1
 !--- Instruct the PIX to hand any traffic destined for 192.168.x.x
 !--- to the router at

 route inside 1
 timeout xlate 1:30:00 conn 1:00:00 half-closed 0:10:00 udp 0:00:00
 timeout rpc 0:10:00 h323 0:05:00
 timeout uauth 0:00:00 absolute
 aaa-server TACACS+ protocol tacacs+
 aaa-server RADIUS protocol radius
 no snmp-server location
 no snmp-server contact
 snmp-server community public
 no snmp-server enable traps
 floodguard enable
 terminal width 200
 : end
 !--- Alternate command:
 !--- conduit permit tcp host eq smtp any
 !--- The conduit command is equivalent to 
 !--- the access-list statements this configuration shows.
 !--- In this case a path known as a conduit is created in order to allow any SMTP 
 !--- traffic to host  Use of this command replaces the 
 !--- access-list and access-group 
 !--- statements that this configuration presents.

Current configuration:
 version 12.0
 service timestamps debug uptime
 service timestamps log uptime
 no service password-encryption
 hostname 2522-R5
 enable secret 5 $1$N0F3$XE2aJhJlCbLWYloDwNvcV.
 ip subnet-zero
 interface Ethernet0
 !--- Sets the IP address of the Ethernet interface to

  ip address
 interface Serial0

  !--- Instructs the serial interface to use 
  !--- the address of the Ethernet interface when the need arises.

  ip unnumbered ethernet 0 
 interface Serial1
  no ip address
  no ip directed-broadcast
 ip classless

 !--- Instructs the router to send all traffic 
 !--- destined for 209.164.3.x to

 ip route

 !--- Instructs the router to send 
 !--- all other remote traffic out serial 0.

 ip route serial 0
 line con 0
  transport input none
 line aux 0
  autoselect during-login
 line vty 0 4
  exec-timeout 5 0
  password ww


There is currently no verification procedure available for this configuration.


The logging console debugging command directs messages to the PIX console. If connectivity to the mail server is a problem, examine the console debug messages to locate the IP addresses of the sending and receiving stations in order to determine the problem.

Information to Collect if You Open a Technical Support Case

If you still need assistance after you complete the troubleshooting steps in this document and want to open a case with Cisco Technical Support, be sure to include this information for troubleshooting your PIX Firewall.
  • Problem description, which includes topology and IP address details of the mail server.
  • Complete any troubleshooting before you open the case.
  • Output from the show tech-support command.
  • Output from the show log command after it runs with the logging buffered debugging command, or console captures that demonstrate the problem (if available)
Attach the collected data to your case in non-zipped, plain text format (.txt). You can attach information to your case by uploading it with the TAC Service Request Tool (registered customers only) . If you cannot access the TAC Service Request Tool, you can send the information in an E-mail attachment to with your case number in the subject line of your message.

Related Information

Updated: Sep 30, 2008
Document ID: 8122