Cisco ASA overview

ASA (Adaptive Security Appliance) is a multipurpose firewall appliance from Cisco. It is built on the same software foundation as Cisco PIX Security Appliances. ASA is usually used for packet filtering purposes, but it supports many additional features, such as stateful filtering, application inspection, NAT, DHCP, routing, VPN, etc. The core operating system for the Cisco ASA family of devices is Cisco ASA Software.

The ASA family of devices include many models. The main standalone appliance model number begins with a 55. Here is a description of some of the models:

• ASA 5505 – an entry level device that comes with a built-in switch that has 8 ports.
• ASA 5510 – comes with 4 built-in routable interfaces and a management Ethernet interface. This model has a slot that supports a compatible module, such as an IPS module.
• ASA 5520, 5540, 5550 – similar to the 5510 model, but with more capacity.
• ASA 5585 – a high-performance, high-capacity model.

The picture below shows a Cisco ASA 5505 appliance (source: Cisco):