Cisco ASA 5505 Configuration – Step by Step

Cisco ASA 5505 Basic Configuration

The Cisco ASA 5505 Firewall is the smallest model in the new 5500 Cisco series of hardware appliances. Although this model is suitable for small businesses, branch offices or even home use, its firewall security capabilities are the same as the biggest models (5510, 5520, 5540 etc).

We assume that our ISP has assigned us a static public IP address (e.g as an example) and that our internal network range is

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.

By default, interface Ethernet0/0 is assigned to VLAN 2 and its 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.

Notice from the diagram that port Ethernet0/0 connects to the Internet and ports Ethernet0/1 to 7 connect to internal hosts (PC computers etc).

Step1: Configure the internal interface vlan

ASA5505(config)# interface Vlan 1
ASA5505(config-if)# nameif inside
ASA5505(config-if)# security-level 100
ASA5505(config-if)# ip address
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
ASA5505(config-if)# no shut

Step 3: Assign Ethernet 0/0 to Vlan 2

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

ASA5505(config)# interface Ethernet0/1
ASA5505(config-if)# no shut

Step 5: Configure PAT on the outside interface

ASA5505(config)# global (outside) 1 interface
ASA5505(config)# nat (inside) 1

UPDATE for ASA Version 8.3 and later

From March 2010, Cisco announced the new Cisco ASA software version 8.3. This version introduced several important configuration changes, especially on the NAT/PAT mechanism. The “global” command is no longer supported. NAT (static and dynamic) and PAT are configured under network objects. The PAT configuration below is for ASA 8.3 and later:

object network obj_any
nat (inside,outside) dynamic interface

Step 6: Configure default route towards the ISP (assume default gateway is

ASA5505(config)# route outside 1

The above steps are the absolutely necessary steps you need to configure for making the appliance operational. Of course there are much more configuration details that you need to implement in order to enhance the security and functionality of your appliance, such as Access Control Lists, Static NAT, DHCP, DMZ zones, authentication etc.

Steps to upgrade your Cisco IOS 

Install TFTP client on the machine is on the same network as of ASA Ethernet 0/1 – inside network. Download Cisco ASA upgrade/ASDMA  files and associate your TFTP default link to the folder containing files.

Connect to TFTP to upload your file by following CLI command

ciscoasa(config)# copy tftp: disk0:

Address or name of remote host []?

Source filename []?

Destination filename []?

Accessing tftp://…!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

27426816 bytes copied in 34.470 secs (806671 bytes/sec)
ciscoasa(config)# copy tftp: flash:

Address or name of remote host []?

Source filename [asa917-32-k8.bin]? asdm-7122.bin

Destination filename [asdm-7122.bin]?

Accessing tftp://…!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Writing file disk0:/asa917-32-k8.bin…

33696792 bytes copied in 41.620 secs (821872 bytes/sec)

ciscoasa(config)# asdm image flash:asdm-7122.bin

ciscoasa(config)# boot system flash:asa917-32-k8.bin
INFO: Converting flash:asa917-32-k8.bin to disk0:/asa917-32-k8.bin
ciscoasa#reload ! restart your machine

ciscoasa(config)# http server enable

ciscoasa(config)# http inside
ciscoasa(config)# copy run start