Document ID: 113305
Updated: Oct 27, 2011
Contents
Introduction
This sample configuration provides information on how to set up the Adaptive Security Appliance (ASA) for access to a mail server located on the outside network.
Refer to ASA 8.3 and Later: Mail (SMTP) Server Access on the DMZ Configuration Example for more information on how to set up the 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 Inside Network Configuration Example in order to set up the ASA Security Appliance for access to a mail/SMTP server located on the Inside network.
Refer to PIX/ASA 7.x and later : Mail (SMTP) Server Access on Outside Network Configuration Example for the identical configuration on Cisco Adaptive Security Appliance (ASA) with versions 8.2 and earlier.
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:
-
Cisco Adaptive Security Appliance (ASA) that runs version 8.3 and later
-
Cisco 1841 Router with Cisco IOS® Software Release 12.4(20)T
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.
Configure
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:
Note: The IP addressing schemes used in this configuration are not legally
routable on the Internet. They are
RFC
1918
addresses that have been used in a lab environment.
The network setup used in this example has the ASA with inside network (192.168.1.0/30) and the outside network (209.64.3.0/30). The mail server with IP address 209.64.3.6 is located in the outside network. Configure NAT statement so that any traffic from the 192.168.2.x network that passes from the inside interface (Ethernet0) to the outside interface (Ethernet 1) translates to an address in the range of 209.64.3.129 through 209.64.3.253. The last available address (209.64.3.254) is reserved for Port Address Translation (PAT) .
Configurations
This document uses these configurations:
| ASA |
|---|
ASA#show run : Saved : ASA Version 8.3(1) ! hostname ASA enable password 8Ry2YjIyt7RRXU24 encrypted passwd 2KFQnbNIdI.2KYOU 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 ! !--- Configure the inside interface. interface Ethernet3 nameif inside security-level 100 ip address 192.168.1.1 255.255.255.252 ! !--- Configure 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 boot system disk0:/asa831-k8.bin ftp mode passive pager lines 24 mtu inside 1500 mtu outside 1500 no failover no asdm history enable arp timeout 14400 !--- This command states 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. object network obj-209.64.3.129_209.64.3.253 range 209.64.3.129-209.64.3.253 !--- 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. object network obj-209.64.3.254 host 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 ASA, no !--- static commands are needed. object-group network nat-pat-group network-object object obj-209.64.3.129_209.64.3.253 network-object object obj-209.64.3.254 object network obj-192.168.2.0 subnet 192.168.2.0 255.255.255.0 nat (inside,outside) dynamic nat-pat-group !--- Creates a static route for the 192.168.2.x network with 192.168.1.2. !--- The ASA 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 ASA 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 12.4 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 ASA-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 ASA. 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 12.4 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 ASA-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 ASA global pool) to the ASA 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 ASA 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.
ciscoasa(config)# policy-map global_policy ciscoasa(config-pmap)#class inspection_default ciscoasa(config-pmap-c)#no inspect esmtp ciscoasa(config-pmap-c)#exit ciscoasa(config-pmap)#exit
Verify
There is currently no verification procedure available for this configuration.
Troubleshoot
The Output Interpreter Tool (registered customers only) (OIT) supports certain show commands. Use the OIT to view an analysis of show command output.
The logging buffered 7 command directs messages to the ASA 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
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Refer to Cisco Technical Tips Conventions for information on conventions used in this document.