The firewall policy is the axis around which most features of the FortiGate firewall revolve. Many settings in the firewall end up relating to or being associated with the firewall policies and the traffic that they govern. Any traffic going through a FortiGate unit has to be associated with a policy. These policies are essentially discrete compartmentalized sets of instructions that control the traffic flow going through the firewall. These instructions control where the traffic goes, how it’s processed, if it’s processed, and even whether or not it’s allowed to pass through the FortiGate.
When the firewall receives a connection packet, it analyzes the packet’s source address, destination address, and service (by port number). It also registers the incoming interface, the outgoing interface it needs to use, and the time of day. Using this information, the FortiGate firewall attempts to locate a security policy that matches the packet. If it finds a policy that matches the parameters, it then looks at the action for that policy. If it is Accept, the traffic is allowed to proceed to the next step. If the Action is Deny or a match cannot be found, the traffic is not allowed to proceed.
The two basic actions at the initial connection are either Accept or Deny:
- If the Action is Accept, the policy action permits communication sessions. There may be other packet processing instructions, such as requiring authentication to use the policy or restrictions on the source and destination of the traffic.
- If the Action is Deny, the policy action blocks communication sessions, and you can optionally log the denied traffic. If no security policy matches the traffic, the packets are dropped. A Deny security policy is needed when it is required to log the denied traffic, also called violation traffic.
One other action can be associated with the policy:
- IPsec – This is an Accept action that is specifically for IPsec VPNs.
In addition to the Accept or Deny actions, there can be a number of instructions associated with a FortiGate firewall, some of which are optional. Instructions on how to process the traffic can include such things as:
- Logging traffic. l l Network Address Translation or Port Address Translation. l Use Virtual IPs or IP Pools. l Caching. l Whether the source of the traffic is based on address, user, device, or a combination. l Whether to treat as regular traffic or IPsec traffic. l What certificates to use. l Security profiles to apply.
- Proxy Options. l Traffic Shaping.
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