ASA 5500 Adding a DMZ Step By Step

Thanks to: http://www.petenetlive.com/

Problem

Assuming you have a working ASA 5500 and you want to add a DMZ to it, this is the process.

Assumptions

1. Networks,

a. Inside network is 10.1.0.0 255.255.0.0
b. Outside network is 123.123.123.120 255.255.255.248
c. DMZ network is 172.16.1.0 255.255.0.0

2. Interfaces,

a. Inside Interface is 10.1.0.254
b. Outside Interface is 172.16.1.254
c. DMZ Interface is 172.16.1.254

3. The Web server in the DMZ will have the following IP addresses,

a. DMZ IP address 172.16.1.1
b. Public IP address 123.123.123.124

4. From the Internet you want to allow web traffic and secure web traffic (http/www andhttps/ssl) to the DMZ Server.

5. The DMZ Server needs to speak to a database server on the inside LAN, on TCP port 1433.

Solution

1. Firstly connect to the ASA log in and go to enable mode.

User Access Verification

Password:
Type help or '?' for a list of available commands.
PetesASA> en
Password: ********

2. Go to configure terminal mode and set up the DMZ interface (In this case Ethernet0/2).

PetesASA# conf t
PetesASA(config)# interface Ethernet0/2
PetesASA((config-if)# nameif DMZ
PetesASA((config-if)# security-level 50
PetesASA((config-if)# ip address 172.16.1.254 255.255.0.0
PetesASA((config-if)# no shutdown
PetesASA((config-if)# exit

3. I like to name the DMZ entities IP addresses so things look neat.

PetesASA(config)# name 172.16.1.1 DMZ-Host-Private-IP
PetesASA(config)# name 123.123.123.124 DMZ-Host-Public-IP

4. Set a some NAT statement to handle traffic flow. (assuming you have a matching global statement like global (outside) 1 xxx - "show run global" will tell you).

PetesASA(config)# nat (DMZ) 1 0.0.0.0 0.0.0.0

Note We are only going to have one DMZ host, and it will have a static mapping - if you had many DMZ hosts then also add "global (DMZ) 1 interface".

5. Now add some static mappings.

PetesASA(config)# static (DMZ,outside) DMZ-Host-Public-IP DMZ-Host-Private-IP netmask 255.255.255.255
PetesASA(config)# static (inside,DMZ) 10.1.0.0 10.1.0.0 netmask 255.255.0.0
PetesASA(config)# static (inside,DMZ) 172.16.1.0 172.16.1.0 netmask 255.255.255.0

6. To let people from outside you need to either create an access-list or add some rules to any existing inbound access-list. ("show run access-group" will tell you, look for an ACL applies "in" to the outside interface e.g. "access-group outbound in interface inside". We will assume I don'thave one so i'll need the access-group at the end.

PetesASA(config)# access-list inbound extended permit tcp any host DMZ-Host-Public-IP eq www
PetesASA(config)# access-list inbound extended permit tcp any host DMZ-Host-Public-IP eq https
PetesASA(config)# access-group inbound in interface outside

7. Now to allow the DMZ host to get to the database server I'm going to allow TCP 1433.

PetesASA(config)# access-list DMZ_outbound extended permit tcp host DMZ-Host-Private-IP host DMS-SQL eq 1433
PetesASA(config)# access-group DMZ_outbound in interface DMZ

8. Finally save the configuration.

PetesASA(config)# write mem
Building configuration...
Cryptochecksum: 5417d5a1 bee8b082 16c6f19d b3839f13

9379 bytes copied in 1.410 secs (9379 bytes/sec)
[OK]