HA CARP + NAT 1 to 1 (Virtual IP) - Packet loss (backup server managing response)



  • Hi everyone,

    Strange issue here - we have two PFsense configured with CARP - seems to work perfectly fine.

    All our server traffic goes trough the PFSense.
    Without NAT rule, everything works fine - master PFSense is handling request and reponse.

    When we add a NAT rule 1 to 1 to one of our server in the LAN we have a HUGE problem...

    • PFSense Master does the "echo"
    • PFSense Backup receives the "reply" > we are then loosing 1 packet - it seems to have a cache because other packets are OK.
    • It seems that the packet is lost between than WAN and the LAN

    You can see the problem here

    Master server
    alt text
    alt text

    Backup server
    alt text
    alt text

    Thank you for your help


  • LAYER 8 Netgate

    Outline exactly what is where, what is pinging what, and what you think is responding erroneously.

    Be specific about what IP address is what.



  • Hi,

    Didn't you seen the screenshots? Everything is explained. Outgoing traffic was done by the master and incoming (reply from server) was going trough the backup.

    Finaly after one week of investigation - we've found the problem.

    In the Virtual IP defined (used after in NAT 1..1) we've specified the "WAN" interface instead of the WAN CARP interface

    I think it would be a great idea to put this information in the troubleshooting guide.