This sample configuration demonstrates how 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 and above: Mail (SMTP) Server Access on the DMZ Configuration Example for more information on how to set up the PIX/ASA Security Appliance for access to a mail/SMTP server located on the DMZ network.
Refer to PIX/ASA 7.x with Mail Server Access on Outside Network Configuration Exampleto set up the PIX/ASA Security Appliance for access to a mail/SMTP server located on the Outside network.
Refer to ASA 8.3 and Later: Mail (SMTP) Server Access on Inside Network Configuration Example for more information on the identical configuration on Cisco Adaptive Security Appliance (ASA) with version 8.3 and later.
Note: Refer to the Cisco Secure PIX Firewall documentation for more information to learn more on how to configure for Microsoft Exchange. Choose your software version, then go to the configuration guide and read the chapter on how to configure for Microsoft Exchange.
There are no specific requirements for this document.
The information in this document is based on these software and hardware versions:
PIX Security Appliance 535
PIX Firewall software release 7.1(1)
Cisco 2500 Series 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.
Refer to the Cisco Technical Tips Conventions for more information on document conventions.
This document can also be used with the Cisco 5500 Series Adaptive Security Appliance (ASA) with Software Version 7.x and later.
In this section, you are presented with the information to configure the features described in this document.
This document uses this network setup:
This document uses these configurations:
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 192.168.1.1 255.255.255.0 ! !--- Define the IP address for the outside interface. interface Ethernet4 nameif outside security-level 0 ip address 126.96.36.199 255.255.255.252 ! interface Ethernet5 shutdown no nameif no security-level no ip address ! passwd 2KFQnbNIdI.2KYOU encrypted ftp mode passive !--- Create an access list that permits Simple !--- Mail Transfer Protocol (SMTP) traffic from anywhere !--- to the host at 188.8.131.52 (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. access-list smtp extended permit tcp any host 184.108.40.206 eq smtp pager lines 24 mtu inside 1500 mtu outside 1500 no failover no asdm history enable arp timeout 14400 !--- Specify that any traffic that originates inside from the !--- 192.168.2.x network NATs (PAT) to 220.127.116.11 if !--- such traffic passes through the outside interface. global (outside) 1 18.104.22.168 nat (inside) 1 192.168.2.0 255.255.255.0 !--- Define a static translation between 192.168.2.57 on the inside and !--- 22.214.171.124 on the outside. These are the addresses to be used by !--- the server located inside the PIX Firewall. static (inside,outside) 126.96.36.199 192.168.2.57 netmask 255.255.255.255 !--- Apply the access list named smtp inbound on the outside interface. access-group smtp in interface outside !--- Instruct the PIX to hand any traffic destined for 192.168.x.x !--- to the router at 192.168.1.2. route inside 192.168.0.0 255.255.0.0 192.168.1.2 1 !--- Set the default route to 188.8.131.52. !--- The PIX assumes that this address is a router address. route outside 0.0.0.0 0.0.0.0 184.108.40.206 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 as "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 netbios inspect rsh inspect rtsp inspect skinny inspect esmtp inspect sqlnet inspect sunrpc inspect tftp inspect sip inspect xdmcp ! !--- SMTP/ESMTP is inspected as "inspect esmtp" is included in the map. service-policy global_policy global Cryptochecksum:f96eaf0268573bd1af005e1db9391284 : end
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 220.127.116.11. ip address 18.104.22.168 255.255.255.252 ! 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 22.214.171.124. ip route 126.96.36.199 255.255.255.0 188.8.131.52 !--- Instructs the router to send !--- all other remote traffic out serial 0. ip route 0.0.0.0 0.0.0.0 serial 0 ! ! line con 0 transport input none line aux 0 autoselect during-login line vty 0 4 exec-timeout 5 0 password ww login ! end
Note: The Router A configuration is not added. You only have to give the IP addresses on the interfaces and set the default gateway to 192.168.1.1, which is the inside interface of the PIX Firewall.
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. Refer to Cisco bug ID CSCtn08326 (registered customers only) for more information.
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
Note: In ASA version 8.0.3 and later, the allow-tls command is available to allow TLS email with inspect esmtp enabled as shown:
policy-map type inspect esmtp tls-esmtp parameters allow-tls inspect esmtp tls-esmtp
If the volume of emails comes in too fast for the internal server, you can use the static command in order to throttle down the PIX to allow a limited number of emails (connections) at a time.
This is an example :
static (inside,outside) 184.108.40.206 192.168.2.57 netmask 255.255.255.255 60 0
This static command example is taken from the PIX Configuration. This command limits the maximum number of connections to 60 for emails.
The maximum number of simultaneous TCP connections that the local IP hosts are to allow is 0, the default, which means unlimited connections. Idle connections are closed after the time specified by the timeout conn command.
Note: If there are intermittent connectivity issues with mail server, make sure that the sysopt noproxyarp inside command is present in the configuration. Otherwise, add it to the configuration. Refer to Cisco Security Appliance Command Reference, Version 8.0 for more information about this command.
There is currently no verification procedure available for this configuration.
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.
|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 to troubleshoot your PIX Firewall.|
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Refer to Cisco Technical Tips Conventions for information on conventions used in this document.