03-28-2005 09:04 PM - edited 02-21-2020 12:02 AM
I am having trouble configuring my Cisco pix 501 to work with my mail server.To start of I will describe my environment.
I have a DLS router to connect to the internet. I connect the Pix to the DSL router then connect the pix to a switch. On the switch I have the mail server and several clients. IP address are the following.
DSL Router Internal: 10.10.10.1
Pix External: 10.10.10.2
Pix internal: 20.20.20.1
Mail server: 20.20.20.10
Client network: 20.20.20.0
MX record: 192.168.2.2
The DSL router has a route on its route table to send any traffic for 20.20.20.0 255.255.255.0 to 10.10.10.2 (the external interface of the cisco pix)
The DSL router has a port forward for port 25 to 20.20.20.10. This worked with out the firewall when I had the mail server plugged into the DSL router and I changed the mail server IP address to 10.10.10.10 (the port forward was 25 -> 10.10.10.10 in this test)
This is the configuration I have on the cisco Pix firewall. I copied the configuration from http://www.cisco.com/en/US/products/hw/vpndevc/ps2030/products_configuration_example09186a0080094466.shtml with the changes listed and reasons below.
PIX Version 6.3(4)
interface ethernet0 auto
interface ethernet1 100full
nameif ethernet0 outside security0
nameif ethernet1 inside security100
enable password XXXXXX encrypted
passwd XXXXXX encrypted
hostname Pix
domain-name Cisco.com
fixup protocol dns maximum-length 512
fixup protocol ftp 21
fixup protocol h323 h225 1720
fixup protocol h323 ras 1718-1719
fixup protocol http 80
fixup protocol rsh 514
fixup protocol rtsp 554
fixup protocol sip 5060
fixup protocol sip udp 5060
fixup protocol skinny 2000
fixup protocol smtp 25
fixup protocol sqlnet 1521
fixup protocol tftp 69
names
access-list mysmtp permit tcp any host 20.20.20.10 eq smtp
pager lines 24
mtu outside 1500
mtu inside 1500
ip address outside 10.10.10.2 255.255.255.0
ip address inside 20.20.20.1 255.255.255.0
ip audit info action alarm
ip audit attack action alarm
pdm logging informational 100
pdm history enable
arp timeout 14400
global (outside) 1 interface
nat (inside) 1 0.0.0.0 0.0.0.0 0 0
access-group mysmtp in interface outside
route outside 0.0.0.0 0.0.0.0 10.10.10.1 1
timeout xlate 0:05:00
timeout conn 1:00:00 half-closed 0:10:00 udp 0:02:00 rpc 0:10:00 h225 1:00:00
timeout h323 0:05:00 mgcp 0:05:00 sip 0:30:00 sip_media 0:02:00
timeout uauth 0:05:00 absolute
aaa-server TACACS+ protocol tacacs+
aaa-server TACACS+ max-failed-attempts 3
aaa-server TACACS+ deadtime 10
aaa-server RADIUS protocol radius
aaa-server RADIUS max-failed-attempts 3
aaa-server RADIUS deadtime 10
aaa-server LOCAL protocol local
http server enable
http 20.20.20.0 255.255.255.0 inside
no snmp-server location
no snmp-server contact
snmp-server community public
no snmp-server enable traps
floodguard enable
telnet 20.20.20.0 255.255.255.0 inside
telnet timeout 5
ssh timeout 5
console timeout 0
dhcpd address 20.20.20.2-20.20.20.254 inside
dhcpd lease 3600
dhcpd ping_timeout 750
dhcpd auto_config outside
terminal width 80
Cryptochecksum:181cc440c44ce21a49c936a0d97a6adb
: end
The differences between the web configuration and mine
I am not using NAT so I left the default.
I have not added a static route for MX record to internal IP address. Do I need to do this on the firewall? For example static (inside,outside) 20.20.20.10 192.168.2.2 netmask 255.255.255.255?
I did not do a route inside as I do not have a router on the inside of the firewall.
I have tried a n fixup protocol smtp bit this did not fix the issue.
A few other things to note. All traffic inside the firewall can get to the internet. For example I can surf the net on the mail server. If I try to telnet to 20.20.20.10 25 on anything inside the firewall it works. If I try it from anything outside the firewall it does not work.
If any one can point me in the right direction it would be great
03-28-2005 10:49 PM
Hi,
Historically the PIX has been a NAT device, beside a Firewall, so that means that even if you are bypassing NAT, you have to specify a NAT rule for that... In other words, if you want to bypass NAT for your mail server, for access from the outside, then you have to tell the PIX to do so. Inbound traffic is only allowed if you have a "bi-directional" NAT rule, which can be accomplished with an static statement (identity NAT) or a NAT 0 + ACL statement:
static (inside,outside) 20.20.20.10 20.20.20.10
or,
access-list nonat permit ip host 20.20.20.10 any
nat (inside) 0 access-list nonat
Of course, this is not all; you also need to allow or open the desired ports/protocols on the outside interface (with an ACL, which you already have).
Now, regarding the MX-Record, if it is pointing to 192.168.2.2, then you might want to NAT the internal mail server to that IP:
static (inside,outside) 192.168.2.2 20.20.20.10
And, make sure that the DSL router routes all traffic destined to 192.168.2.2 to the PIX.
Hope that helps!
Federico Rodriguez
03-29-2005 08:41 PM
Hi Federico,
Yes that did help thank you. mail traffice is now coming and going.
Thanks
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