Bug #9594

pfSense caused asymmetric routing, blocks traffic

Added by Louis van Breda about 1 year ago. Updated about 1 year ago.

Not a Bug
Target version:
Start date:
Due date:
% Done:


Estimated time:
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I divided my network in multiple subnets. There is traffic between those subnets passing the LAN gateways and related rules. That traffic is largely blocked by the firewall due to “TCP:S”.

I have been investigating the problem and my conclusion is that pf sense handles the traffic between two subnets (LAN-A) and (LAN-B) as follows:
- System-x on LAN-A (192.168.1.x) sends trys to send something to an address in LAN-B (192.168.2.y)
(192.168.1.x to (LAN-A-GW))
- Lan-A-GW knows from the routing table where 192.168.2.y is and send it to that route
( to 192.168.2.y)
The response follows the same methodology
- 192.168.2.y to
- to 192.168.1.x
As you can see that are two different routes ==> TCP:S ==> Blocked

The route * should * IMHO have been
- 192.168.1.x to
- * to *
- to 192.168.2.y

So traffic towards another LAN * should * IMHO always! Go via the corresponding LAN-gateway !

That would:
1. Solve the asymmetric routing problem (do not know how to solve that!) AND
2. Would allow the LAN-B gateway to check if the incoming traffic is (in the B-LAN’s opinion) allowed!

In the actual FW setup, your neighbor LAN’s(GW) determine what is allowed to reach your LAN (house) Crazy IMHO !!!

Tested on actual 2.4.4 release 3 version


Note that I did some serious investigation to analyze the problem, and did write some more details in the forum. However the essence is described over here


#1 Updated by Jim Pingle about 1 year ago

  • Status changed from New to Not a Bug
  • Priority changed from High to Normal

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