Access Control Lists

Question 1

Access Control Lists

Answer 1

• Used to allow or deny traffic
  
  • Also used for NAT, QoS, etc.
• Defined on the ingress or egress of an interface
  
  • Incoming or outgoing

• ACLs can evaluate on certain criteria
• Source IP, Destination IP, TCP port numbers, UDP
port numbers, ICMP

• Deny or permit
  
  • What happens when an ACL matches the traffic?

• ACLs have evolved through the years
• More options and features available for traffic
filtering

Question 2

Firewall rules

Answer 2

• Access control lists (ACLs)
• Allow or disallow traffic based on tuples
• Groupings of categories
• Source IP, Destination IP, port number, time of day,
application, etc.

• A logical path
  
  • Usually top-to-bottom
• Can be very general or very specific
  
  • Specific rules are usually at the top
• Implicit deny
  
  • Most firewalls include a deny at the bottom
  • Even if you didn’t put one