Asymmetric Routing Not Work Well

  • Hello All,


    One question, I use pfSense ver. 2.2 with 4 interfaces.

    1 - WAN (Global Static /28)
    2 - LAN (179.0/24)
    3 - OPT1(188.0/24)
    4 - OPT2(189.0/24)

    Traffic between same Interface (e.g. OPT1 to OPT1) as shown below blocking TCP:SA:

    Firewall rule pass everything to OPT1 as shown below:

    I have tried:
    1 - Asymmetric Routing

    But still blocking all TCP:SA traffic.


  • LAYER 8 Global Moderator

    Why would you have asymmetric routing between 2 interfaces on pfsense?

    Looks like you got some sort of mask issue.. Why would pfsense even see traffic from to or vice versa?

    Looks like the same network to me..  Did you bridge interfaces?  Pfsense sure shouldn't be seeing that traffic, why are you sending traffic through pfsense to get to the same network?

    I would guess that .221 sent traffic to .220 over the switch, and then for some unknown reason .220 is trying to send back its syn,ack via pfsense even though the source IP per your info is on the same segment and should not be sending that traffic to pfsense.  You have the wrong mask on .220?

  • PFSense is a stateful firewall, not a dump router. Asymmetric paths means the states are never acknowledged. SYN goes in one interface, but that interface never see the SYN-ACK because it came back in a different interface. PFSense will reject these out of state packets by default.

  • Dears johnpoz and Harvy66,

    Thank's your replay is very helpful.

    Yes, as johnpoz posted the problem is mask issue on server side.


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