PIX/ASA 7.x and Later: Mail (SMTP) Server Access on Outside Network Configuration Example

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Updated:February 4, 2020
Document ID:70029

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    Introduction

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

    Refer to PIX/ASA 7.x and above : Mail Server Access on Inside Network Configuration Example in order to set up the PIX/ASA Security Appliance for access to a mail/SMTP server located on the Inside network.

    Refer to PIX/ASA 7.x with Mail Server Access on DMZ Network Configuration Example in order to set up the PIX/ASA Security Appliance for access to a mail/SMTP server located on the DMZ network.

    Refer to ASA 8.3 and Later: Mail (SMTP) Server Access on Outside Network Configuration Example for more information on the identical configuration on Cisco Adaptive Security Appliance (ASA) with version 8.3 and later.

    Refer to the Cisco Secure PIX Firewall documentation for further information about how to set Microsoft Exchange. Choose your software version, then go to the configuration guide and read the chapter on how to configure for Microsoft Exchange.

    Prerequisites

    Requirements

    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 535

    • PIX Firewall software release 7.1(1)

    • Cisco 2500 Routers

    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.

    Conventions

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

    Related Products

    This configuration can also be used with an Adaptive Security Appliance (ASA) that runs version 7.x and later.

    Configure

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

    Note: Use the Cisco CLI Analyzer to obtain more information on the commands used in this section.

    Network Diagram

    This document uses this network setup:

    pix-mailserver-outside-1.gif

    Configurations

    This document uses these configurations:

    PIX Firewall 
    PIX Version 7.1(1) 
!
hostname pixfirewall
enable password 8Ry2YjIyt7RRXU24 encrypted
names
!
interface Ethernet0
 shutdown
 no nameif
 no security-level
 no ip address
!
interface Ethernet1
 shutdown
 no nameif
 no security-level
 no ip address
!
interface Ethernet2
 shutdown
 no nameif
 no security-level
 no ip address
!


!--- Define the IP address for the inside interface.
 
interface Ethernet3
 nameif inside
 security-level 100
 ip address 192.168.1.1 255.255.255.252 
!


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

interface Ethernet4
 nameif outside
 security-level 0
 ip address 209.64.3.1 255.255.255.252 
!
interface Ethernet5
 shutdown
 no nameif
 no security-level
 no ip address
!
passwd 2KFQnbNIdI.2KYOU encrypted
ftp mode passive
pager lines 24
mtu inside 1500
mtu outside 1500
no failover
no asdm history enable
arp timeout 14400


!--- This command defines the global for the Network Address Translation !--- (NAT) statement. In this case, the two commands state that any traffic !--- from the 192.168.2.x network that passes from the inside interface (Ethernet0) !--- to the outside interface (Ethernet 1) translates into an address !--- in the range of 209.64.3.129 through 209.64.3.253 and contains a subnet !--- mask of 255.255.255.128.


global (outside) 1 209.64.3.129-209.64.3.253 netmask 255.255.255.128


!--- This command reserves the last available address (209.64.3.254) for !--- for Port Address Translation (PAT). In the previous statement, !--- each address inside that requests a connection uses one !--- of the addresses specified. If all of these addresses are in use, !--- this statement provides a failsafe to allow additional inside stations !--- to establish connections.


global (outside) 1 209.64.3.254


!--- This command indicates that all addresses in the 192.168.2.x range !--- that pass from the inside (Ethernet0) to a corresponding global !--- designation are done with NAT. !--- As outbound traffic is permitted by default on the PIX, no !--- static commands are needed.


nat (inside) 1 192.168.2.0 255.255.255.0


!--- Creates a static route for the 192.168.2.x network with 192.168.1.2. !--- The PIX forwards packets with these addresses to the router !--- at 192.168.1.2. 

route inside 192.168.2.0 255.255.255.0 192.168.1.2 1


!--- Sets the default route for the PIX Firewall at 209.64.3.2.


route outside 0.0.0.0 0.0.0.0 209.64.3.2 1
timeout xlate 3:00:00
timeout conn 1:00:00 half-closed 0:10:00 udp 0:02:00 icmp 0:00:02
timeout sunrpc 0:10:00 h323 0:05:00 h225 1:00:00 mgcp 0:05:00
timeout mgcp-pat 0:05:00 sip 0:30:00 sip_media 0:02:00
timeout uauth 0:05:00 absolute
no snmp-server location
no snmp-server contact
snmp-server enable traps snmp authentication linkup linkdown coldstart
telnet timeout 5
ssh timeout 5
console timeout 0
!
class-map inspection_default
 match default-inspection-traffic
!
!


!--- SMTP/ESMTP is inspected since "inspect esmtp" is included in the map.


policy-map global_policy
 class inspection_default
  inspect dns maximum-length 512 
  inspect ftp 
  inspect h323 h225 
  inspect h323 ras 
  inspect rsh 
  inspect rtsp 
  inspect esmtp 
  inspect sqlnet 
  inspect skinny 
  inspect sunrpc 
  inspect xdmcp 
  inspect sip 
  inspect netbios 
  inspect tftp 
!


service-policy global_policy global
Cryptochecksum:8a63de5ae2643c541a397c2de7901041
: end

    Router A 
    Current configuration:
  !
  version 12.0
  service timestamps debug uptime
  service timestamps log uptime
  no service password-encryption
  !
  hostname 2522-R4
  !
  enable secret 5 $1$N0F3$XE2aJhJlCbLWYloDwNvcV.
  !
  ip subnet-zero
  !
  !
  !
  !
  !
  interface Ethernet0
   

!--- Assigns an IP address to the inside Ethernet interface.


   ip address 192.168.2.1 255.255.255.0
   no ip directed-broadcast
  !
  interface Ethernet1
   

!--- Assigns an IP address to the PIX-facing interface.


   ip address 192.168.1.2 255.255.255.252
   no ip directed-broadcast
  !
  interface Serial0
   no ip address
   no ip directed-broadcast
   shutdown
  !
  interface Serial1
   no ip address
   no ip directed-broadcast
   shutdown
  !
  ip classless
  

!--- This route instructs the inside router to forward all !--- non-local packets to the PIX.


  ip route 0.0.0.0 0.0.0.0 192.168.1.1
  !
  !
  line con 0
   transport input none
   line aux 0
   autoselect during-login
   line vty 0 4
   exec-timeout 5 0
   password ww
   login
  !
  end

    Router B 
    Current configuration:
  !
  version 12.0
  service timestamps debug uptime
  service timestamps log uptime
  no service password-encryption
  !
  hostname 2522-R4
  !
  enable secret 5 $1$N0F3$XE2aJhJlCbLWYloDwNvcV.
  !
  ip subnet-zero
  !
  !
  !
  !
  interface Ethernet0
   

!--- Assigns an IP address to the PIX-facing Ethernet interface.


   ip address 209.64.3.2 255.255.255.252
   no ip directed-broadcast
  !
  interface Ethernet1
   

!--- Assigns an IP address to the server-facing Ethernet interface.


   ip address 209.64.3.5 255.255.255.252
   no ip directed-broadcast
  !
  interface Serial0
   

!--- Assigns an IP address to the Internet-facing interface.


   ip address 209.64.3.9 255.255.255.252
   no ip directed-broadcast
   no ip mroute-cache
  !
  interface Serial1
   no ip address
   no ip directed-broadcast
  !
  ip classless
  

!--- All non-local packets are to be sent out serial 0. In this case, !--- the IP address on the other end of the serial interface is not known, !--- or you can specify it here.


  ip route 0.0.0.0 0.0.0.0 serial 0
  !
  

!--- This statement is required to direct traffic destined to the !--- 209.64.3.128 network (the PIX global pool) to the PIX to be translated !--- back to the inside addresses.


  ip route 209.64.3.128 255.255.255.128 209.64.3.1
  !
  !
  line con 0
   transport input none
  line aux 0
   autoselect during-login
  line vty 0 4
   exec-timeout 5 0
   password ww
   login
  !
  end

    ESMTP TLS Configuration

    Note: If you use Transport Layer Security (TLS) encryption for e-mail communication then the ESMTP inspection feature (enabled by default) in the PIX drops the packets. In order to allow the e-mails with TLS enabled, disable the ESMTP inspection feature as this output shows.

    pix(config)#policy-map global_policy
pix(config-pmap)#class inspection_default
pix(config-pmap-c)#no inspect esmtp
pix(config-pmap-c)#exit
pix(config-pmap)#exit

    Verify

    There is currently no verification procedure available for this configuration.

    Troubleshoot

    The Cisco CLI Analyzer supports certain show commands. Use CLI Analyzer to view an analysis of show command output.

    Note: Refer to Important Information on Debug Commands before you use debug commands.

    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.

    Related Information

    Revision History

    Revision Publish Date Comments
    1.0
    04-Feb-2020
    Initial Release

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