Four Major Elements in choosing a Firewall?

Answer 1

firewall functions by acting on traffic based on it's policy. A policy is comprised of a set of rules. A rule is an action taken on traffic that fit a certain criteria. A single rule is comprised of four basic elements:

• Source
• • This is where the IP traffic is coming from and is comprised of the following
  • Single IP address or multiple IP addresses
  • One or more networks in the form of a network ID and subnet mask
  • A combination of IP addresses and Network addresses
• Destination
• • This is where the IP traffic is going to and is comprised of the following
  • Single IP address or multiple IP addresses
  • One or more networks in the form of a network ID and subnet mask
  • A combination of IP addresses and Network addresses
• Service
• • This is the type of protocol that the traffic is using and is comprised of the following
  • One or more destination TCP ports
  • One or more destination UDP ports
  • A group or combination of destination TCP and UDP ports
  • Although source port can be limited to a certain range, it is generally left wide open. It is the destination port that is primarily specified.
• Action
• • The administrator chooses from the following options if all the above three criteria match
  • Reject the traffic
  • Drop the traffic
  • Permit the traffic
  • Encrypt the traffic on IPSEC VPN capable firewalls