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About Firewall

Firewall provides traditional firewall functionality, blocking and/or flagging traffic based on rules. Although the term "Firewall" has grown to encompass many functionalities, the Untangle "Firewall" is a simple traditional firewall used to block and/or flag TCP and UDP sessions using rules.



This section reviews the different settings and configuration options available for Firewall.



The Rules tab allows you to specify rules to Block, Pass or Flag traffic that crosses the Untangle.

The Rules documentation describes how rules work and how they are configured. Firewall uses rules to determine to block/pass the specific session, and if the sessions is flagged. Flagging a session marks it in the logs for reviewing in the event logs or reports, but has no direct effect on the network traffic.

Typically Untangle is installed as a NAT/gateway device, or behind another NAT/gateway device in bridge mode. In this scenario all inbound sessions are blocked by NAT except those explicitly allowed with port forwards. Because of this, the Firewall does not block anything by default. It is up to you to decide to best fit for your network, whether you only want to block specific ports or you want to block everything and allow only a few services.

Rule Actions

  • Pass: Allows the traffic which matched the rule to flow.
  • Block: Blocks the traffic which matched the rule.

Additionally a session can be flagged. If Flag is checked the event is flagged for easier viewing in the event log. Flag is always enabled if the action is Block.

Event Log

Use the following terms and definitions to understand the Event Log:


Timestamp The time the event took place.
Client The IP address of the client that made the request.
Client Port The port used by the client that made the request.
Username The username of the client that made the request, if available.
Blocked True is the session was blocked, false if it was not.
Flagged True is the session was flagged, false if it was not.
Rule ID The ID of the rule that matched this session (or none if it matched no rules)
Server The IP address of the server that received the request.
Server Port The port used by the server that received the request.

Related Topics

User Guide


Firewall FAQs

Why doesn't the Untangle Server's Firewall have any rules enabled by default?

When Untangle is in router mode, it is performing NAT, which blocks all inbound sessions. When Untangle is in bridge mode, the Untangle Server is already behind a firewall, which is doing NAT.


The default is pass all?! Why? That's so insecure!

As explained above, most Untangle boxes are install 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 Untangle) 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.


Where do I add Port Forwards?

Port forwarding is a feature available in Config > Network > Port Forward Rules.


I want to lock-down my network but for a few exceptions. What is the best way to do this?

Simply add a rule with no qualifiers, 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.


Why are my Firewall rules not 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.


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 NATd 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.


Does Firewall use iptables?

No. Firewall has nothing to do with iptables. Firewall rules are not iptables rules.

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