Cisco ASA Security Levels

Lessons Discussion
43

How to open and block ports in a firewall? and why do we do that ?

44

Hello Zahid

It depends on what you mean. If you mean the actual physical ports on the device, then there are several ways to do this.

  1. You can use the security levels that are described in this lesson allowing traffic from a higher security level port to a lower security level port but not the opposite.
  2. You can use access lists to indicate what traffic you want to allow and deny on particular physical ports.
  3. You can add policies on the ASA that say what traffic is allowed on which ports and what is not.

If you mean the ports of the Transport layer, such as TCP or UDP ports, then this can also be achieved using access lists and/or policies on the device. Take a detailed look at the various lessons in the ASA Firewall course below for more information:

I hope this has been helpful!

Laz