Firewalls and Access Control Lists (ACLs)

Firewalls — Dedicated devices for using Access Control Lists (ACLs) to protect networks

Access Control Lists (ACLs)

• Essential for securing networks from unwanted traffic
• Consist of permit and deny statements, often based on port numbers
• Rule sets placed on firewalls, routers, and network infrastructure devices
• Control the flow of traffic into and out of networks
• May define quality of service levels inside the network but are primarily used for network security in firewalls

Configuring ACLs

• A web-based interface or a text-based command line interface can be used
• The order of ACL rules specifies the order of actions taken on traffic (top-down)
• The first matching rule is executed, and no other ACLs are checked
• Place the most specific rules at the top and generic rules at the bottom
• Some devices support implied deny functions, while others require a “deny all” rule at the end
• Actions taken by network devices should be logged, including deny actions

ACL Rules

Made up of some key pieces of information including:

• Type of traffic
• Source of Traffic
• Destination of traffic