ASA 5505, how to configure DMZ to Inside traffic flows

Question

Dear.
We have a Cisco ASA 5505 with an outside, inside and DMZ interface.
We really need all these interfaces.
The DMZ interface has been configured to block any traffic to the inside (restrict traffic flow). This restriction can’t be disable, an error occurred when doing this.
I will allow only one single port has access from DMZ to the inside, is that possible? And how?
Thanks for the feedback.
Regards.
Peter.

Answer 1

What i mean with "can't be disabled": when you navigate to Configuration/interfaces and select the DMZ interface / advanced, you can block traffic. By default Inside has been selected in the drop-down box. However, you can't leave it blank, you need to specify at least one. I can't create another, extra interfaces because the license is 3 max.
So, my question is: can I create a rule somewhere to overwrite this setting for only one specific port? And how?
Result of the command: "show version"
Cisco Adaptive Security Appliance Software Version 8.2(5)
Device Manager Version 6.4(5)
Compiled on Fri 20-May-11 16:00 by builders
System image file is "disk0:/asa825-k8.bin"
Config file at boot was "startup-config"
router up 100 days 1 hour
Hardware:   ASA5505, 512 MB RAM, CPU Geode 500 MHz
Internal ATA Compact Flash, 128MB
BIOS Flash Firmware Hub @ 0xffe00000, 1024KB
Encryption hardware device : Cisco ASA-5505 on-board accelerator (revision 0x0)
                             Boot microcode   : CN1000-MC-BOOT-2.00
                             SSL/IKE microcode: CNLite-MC-SSLm-PLUS-2.03
                             IPSec microcode  : CNlite-MC-IPSECm-MAIN-2.05
0: Int: Internal-Data0/0    : address is a44c.11bb.5492, irq 11
1: Ext: Ethernet0/0         : address is a44c.11bb.548a, irq 255
2: Ext: Ethernet0/1         : address is a44c.11bb.548b, irq 255
3: Ext: Ethernet0/2         : address is a44c.11bb.548c, irq 255
4: Ext: Ethernet0/3         : address is a44c.11bb.548d, irq 255
5: Ext: Ethernet0/4         : address is a44c.11bb.548e, irq 255
6: Ext: Ethernet0/5         : address is a44c.11bb.548f, irq 255
7: Ext: Ethernet0/6         : address is a44c.11bb.5490, irq 255
8: Ext: Ethernet0/7         : address is a44c.11bb.5491, irq 255
9: Int: Internal-Data0/1    : address is 0000.0003.0002, irq 255
10: Int: Not used            : irq 255
11: Int: Not used            : irq 255
Licensed features for this platform:
Maximum Physical Interfaces    : 8        
VLANs                          : 3, DMZ Restricted
Inside Hosts                   : 50       
Failover                       : Disabled
VPN-DES                        : Enabled  
VPN-3DES-AES                   : Enabled  
SSL VPN Peers                  : 2        
Total VPN Peers                : 10       
Dual ISPs                      : Disabled 
VLAN Trunk Ports               : 0        
Shared License                 : Disabled
AnyConnect for Mobile          : Disabled 
AnyConnect for Cisco VPN Phone : Disabled 
AnyConnect Essentials          : Disabled 
Advanced Endpoint Assessment   : Disabled 
UC Phone Proxy Sessions        : 2        
Total UC Proxy Sessions        : 2        
Botnet Traffic Filter          : Disabled 
This platform has a Base license.
Serial Number: xxxxxxxxxxxxxx
Running Activation Key: xxxxxxxxxxxxxxxxxxxxxxxxxxxx
Configuration register is 0x1
Configuration last modified by enable_15 at 14:43:11.295 CEDT Mon Sep 9 2013