Re: DMZ to INSIDE Communication

["Darden, Patrick S." <darden () armc org>]

Your setup description confused me a bit.  Forgive me if I simplify it.

Seems to me you have 4 situations here:

1.  outside-->DmzSmtpIP:25
2.  DmzSmtpIP-->outside:25
3.  inside-->DmzSmtpIP:25
4.  DmzSmtpIP-->inside:25

I.  Check your ACL's first.  Make sure packets are allowed according to the template above.
II. Check your NAT/PAT second.  Make sure that if you are MASQuerading in any way, the interfaceIP you MASQuerade on is 
included in the ACLs in part I.  E.g. if you masq your internal SMTP server's IP address using the external interface 
of your firewall, then make sure you include both the internal SMTP server's IP and the external interface of the 
firewall's IP as well in your ACLs.

I like to turn on ping as well as whatever other protocol I am working on, so I can test via ping at each step.  In 
this case, you can use telnet to port 25 at each step i.e.:

1.  from outside your network, telnet to DmzSmtpIP:25
2.  from your DmzSmtpIP server telnet to any outside smtp server on port 25
3.  from your exchange server on your lan telnet to the DmzSmtpIP:25
4.  from your DmzSmtpIP server telnet to the exchange server on your lan on port 25

--p

-----Original Message-----
From: firewall-wizards-bounces () listserv icsalabs com
[mailto:firewall-wizards-bounces () listserv icsalabs com]On Behalf Of
chris mr
Sent: Thursday, October 11, 2007 5:06 PM
To: firewall-wizards () listserv icsalabs com
Subject: [fw-wiz] DMZ to INSIDE Communication


Hello,

I have an ASA5505 and I'm stumped.  

I have a IIS SMTP server on the DMZ and it is able to communicate with OUTSIDE smtp servers on port 25.  I want it to 
be able to communicate with INSIDE smtp servers, however the packets get dropped.  
WEBSERVER:gt1023---------->DMZ>>>INSIDE---xx--->EXCHANGE:25

Here is the setup:

Interfaces/Vlans:
-Outside 
        security=0
        IP 75.xx.yy.233
-Outside1 
        security=0 ( backup ISP )
        IP 12.xx.yy.154
-Inside 
        security=100
        IP 200.xx.yy.158
-DMZ 
        security=50
        IP 192.168.2.1



Here is my relevant setup:
name 192.168.2.2 WEBSERVER_nat  >> on DMZ interface
name 192.168.2.3 WEBSERVER_nat1 >> on DMZ interfce
name 75.xx.yy.234 WEBSERVER_real >> public IP of web server
name 12.xx.yy.155 WEBSERVER_real1 >> public IP of web server (round-robin DNS setup)
name 200.xx.yy.10 GATEWAY >> MS ISA server on Inside interface
name 200.xx.yy.11 EXCHANGE >> MS Exchange on Inside interface

global (outside1) 2 interface
global (DMZ) 2 interface
global (outside) 2 interface

nat (inside) 2 GATEWAY 255.255.255.255
nat (inside) 2 EXCHANGE 255.255.255.255

static (inside,outside) tcp interface smtp EXCHANGE smtp netmask 255.255.255.255
static (inside,outside1) tcp interface smtp EXCHANGE smtp netmask 255.255.255.255
static (DMZ,outside1) WEBSERVER_real1 WEBSERVER_nat netmask 255.255.255.255 tcp 0 25
static (DMZ,inside) WEBSERVER_real1 WEBSERVER_nat1 netmask 255.255.255.255
static (DMZ,outside) WEBSERVER_real WEBSERVER_nat netmask 255.255.255.255 tcp 0 25
static (DMZ,inside) WEBSERVER_real WEBSERVER_nat netmask 255.255.255.255

access-group ACLIN in interface outside1
access-group ACLIN in interface outside

access-list ACLIN extended deny ip 172.16.0.0 255.255.0.0 interface outside log
access-list ACLIN extended deny ip 192.168.0.0 255.255.0.0 interface outside log
access-list ACLIN extended deny ip 10.0.0.0 255.0.0.0 interface outside log
access-list ACLIN extended deny ip 10.0.0.0 255.0.0.0 interface outside1 log
access-list ACLIN extended deny ip 192.168.0.0 255.255.0.0 interface outside1 log
access-list ACLIN extended deny ip 172.16.0.0 255.255.0.0 interface outside1 log
access-list ACLIN extended permit tcp any host 75.xx.yy.233 object-group INSIDE_services (smtp)
access-list ACLIN extended permit tcp any host 12.xx.yy.154 object-group INSIDE_services (smtp)
access-list ACLIN extended permit icmp any object-group DMZ (WEBSERVER_real and _real1) object-group DMZ_icmp log
access-list ACLIN extended permit icmp any interface outside object-group OUTSIDE_icmp (echo/reply)
access-list ACLIN extended permit icmp any interface outside1 object-group OUTSIDE_icmp
access-list ACLIN extended permit tcp any object-group DMZ object-group DMZ_services (http/https/ftp)
access-list ACLIN extended permit tcp any eq domain object-group DMZ log
access-list ACLIN extended permit udp any eq domain object-group DMZ log
access-list ACLIN extended deny ip any any log


       
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