Firewall FAQ

1. Should I use pre-NAT or post-NAT addresses/ports in Firewall rules?

Firewall rules always match on the address which has more information. In other words, if the entire internal network is being NAT'd from 192.168.*.* to, Firewall will match on the 192.168.*.* for traffic to and from this network. At the session layer this works out to be pre-NAT on source address, post-NAT on destination address, pre-NAT on source port, and post-NAT on destination port. An easy way to remember this is that it always matches where it gets the most information.


2. How do I lock down my network but for a few exceptions via the Firewall application?

Simply add a rule with no conditions, set it to Block, and put it at the bottom of the list. This will match all traffic, so anything not explicitly passed in a rule above it will be blocked.


3. Why aren't my Firewall rules being triggered?

Firewall rules work from top to bottom; the first rule that the traffic matches will fire. If you have a broad rule near the top of your list that is matching, no other rules will be evaluated.


4. Why is the default action in Firewall to pass all?

Most NG Firewall boxes are installed in router mode meaning that NAT is being performed on traffic. This means all inbound traffic is blocked regardless of the settings in the Firewall; only explicitly port-forwarded traffic goes inside your network. Alternatively, most bridge-mode deployments are installed behind a NAT device so the Firewall app (and NG Firewall) will only see traffic that has already explicitly been passed with a port forward on the NAT device. What this means is that the "pass all" default in most scenarios means "block everything inbound but nothing outbound", which is common policy for a lot of organizations. In our opinion most of the Firewall's utility is for controlling outbound traffic, however you are free to add rules controlling inbound, outbound or any other type of traffic you wish.





Was this article helpful?
0 out of 2 found this helpful
Have more questions? Submit a request



Please sign in to leave a comment.

Powered by Zendesk