Cisco ASA 5510 Firewall : Basic Configuration Tutorial

We assume that our ISP has assigned us a static public IP address (e.g 200.200.200.1 as an example) and that our internal network range is 192.168.1.0/24. We will use Port Address Translation (PAT) to translate our internal IP addresses to the public address of the outside interface. The difference of the 5505 model from the bigger ASA models is that it has an 8-port 10/100 switch which acts as Layer 2 only. That is, you can not configure the physical ports as Layer 3 ports, rather you have to create interface Vlans and assign the Layer 2 interfaces in each VLAN. By default, interface Ethernet0/0 is assigned to VLAN 2 and it's the outside interface (the one which connects to the Internet), and the other 7 interfaces (Ethernet0/1 to 0/7) are assigned by default to VLAN 1 and are used for connecting to the internal network. Let's see the basic configuration setup of the most important steps that you need to configure.
Step1: Configure the internal interface vlan
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ASA5505(config)# interface Vlan 1
ASA5505(config-if)# nameif inside
ASA5505(config-if)# security-level 100
ASA5505(config-if)# ip address 192.168.1.1 255.255.255.0
ASA5505(config-if)# no shut

Step 2: Configure the external interface 
vlan (connected to Internet)
ASA5505(config)# interface Vlan 2
ASA5505(config-if)# nameif outside
ASA5505(config-if)# security-level 0
ASA5505(config-if)# ip address 200.200.200.1 255.255.255.0
ASA5505(config-if)# no shut

Step 3: Assign Ethernet 0/0 to Vlan 2
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ASA5505(config)# interface Ethernet0/0
ASA5505(config-if)# switchport access vlan 2
ASA5505(config-if)# no shut

Step 4: Enable the rest interfaces with no shut
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ASA5505(config)# interface Ethernet0/1
ASA5505(config-if)# no shut
Do the same for Ethernet0/1 to 0/7.

Step 5: Configure PAT on the outside interface
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ASA5505(config)# global (outside) 1 interface
ASA5505(config)# nat (inside) 1 0.0.0.0 0.0.0.0

Step 6: Configure default route towards the ISP (assume default gateway is 200.200.200.2)
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ASA5505(config)# route outside 0.0.0.0 0.0.0.0 200.200.200.2 1


The above basic configuration is just the beginning for making the appliance operational. There are many more configuration features that you need to implement to increase the security of your network, such as Static and Dynamic NAT, Access Control Lists to control traffic flow, DMZ zones, VPN etc.