pfSense

Sticky connections in combination with relayd in 2.1 is seriously broken. Take this circumstance, relayd listening on:

IP 1.2.3.4 port 80, redirecting to 192.168.1.10 port 80
IP 1.2.3.5 port 80, redirecting to 192.168.1.15 port 80
IP 1.2.3.6 port 25, redirecting to 192.168.1.14 port 25
IP 1.2.3.7 port 25, redirecting to 192.168.1.20 port 25

If sticky is enabled, when you connect to 1.2.3.4:80 sourced from IP 4.3.2.1, every connection sourced from 4.3.2.1 from that point on will be redirected to 192.168.1.10. For instance, from 4.3.2.1, connecting to 1.2.3.5:80 will go to 192.168.1.10:80. Going to 1.2.3.6:25 will go to 192.168.1.10:25. The IP that's being connected to gets completely ignored from that point on.