Firewall rule to pass everything, however it is blocking TCP:SA/FA/R/RA/PA



  • I am seeing a strange problem when connecting to a number of hosts, where the default gateway is a pfSense 2.0 box.

    I can at first connect to the hosts (SSH/HTTP/HTTPS) then after around 60 seconds then the connection drops.

    So when looking at the logs, I can see the initial connection (I have switched logging packets on for matches) and then after aroudn a minutes I start to see pfsense blocking the connections, and the only thing I can see different is some of the TCP flags are set (namely SA/FA/R/RA)

    Anyone got any ideas why it initially passes the traffic then once it starts to see these flags it drops them?

    Thanks in advance for any help

    Rich


  • Rebel Alliance Developer Netgate

    Most common cause of that is asymmetric routing: Traffic goes out one way and comes back in a different way. Because the firewall only sees half the connection, it doesn't know it's valid, and drops the traffic.

    If you notice that all of what you are seeing blocked is "return" traffic - that is, what the other side is expecting to get back after an initial connection in the handshake (> SYN, < SYN/ACK, > ACK).



  • That makes sense, I at least have somewhere to start looking now

    Thanks for your help.


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