Static routes causing TCP retransmissions

  • Scenario:
    There are two routers. Router A is the gateway to our MPLS, Router B is the pfsense and is our broadband gateway. Router A is, Router B is the LAN of router A is plugged into the LAN of router B. There is a static route in Router B pointing MPLS traffic to router A which then sends it out to the MPLS, and there is a static route on Router A pointing Internet traffic to Router B.

    The issue was identified during the process of setting up failover between the Broadband and the MPLS. For a user at this site there are 3 potential paths that they can use to RDP to a certain server. Path A is using Router A as the gateway, which then goes straight over the MPLS to the server. Path B uses Router B as the gateway and then goes over the broadband connection to a port forward on the other end. Path C uses Router B as the gateway, which then forwards the traffic to Router A via a static route.

    Paths A and B work great. Path C is constantly disconnecting and reconnecting (this is actually happening to several applications, not just RDP). After reviewing a wireshark of each path, Path C using the static route would intermittently have clumps of TCP Retransmissions that that other paths do not have.  Unfortunately we NEED Path C to work, I wanted to know if anyone has seen this issue with Static Routes on the Zywall 5/pfsense or if anyone has any insight. HELP!!

  • Martin,

    I am still investigating what is exact;ly happening with our pfSense-2.1.4-RELEASE(amd64).
    We are in a  similar situation as your setup,,other than our pfSense is staic routed to an ip phone and a teacher segment lan router that has wokred fine with pfSense-1.2.3 and pfSense-2.0.1 but with pfSense-2.1.4 i am seeing lots of traffic blocked in the fiewrall logs and i am very certain the lan and OPT inerface rules should be passing all traffic,,between lans. If I disable the static route temporarily,,this blocking stops (in the firewall logs)?
    I'm not real smart but if i spend enough time on something i can usually hammer it out.
    What we are suffering from is on a Windows domain dns wins smb is being blocked,,,with this scenario. Not good in a production setting.

    I need to get wireshark on my setup,ro see were the packets are getting confused at.
    I setup two other pfSense machines at two of our other school buildings at the same time,with a  much simpler setup,,and couldnt have been any easier to setup.



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