Forum Discussion

mreco_159588's avatar
Jun 08, 2017

No response after added virtual server IP address as floating self-IP address

Hi,   I have an F5 HA pair that serves several virtual servers.   VS1: ip1   VS2: ip2   Now, the IP address of VS1 (ip1) was already defined as a floating self-IP, but I found out that th...
  • mreco_159588's avatar
    Jun 14, 2017

    It was driving me nuts, since I just want to understand what's going.

     

    After reading this post: https://devcentral.f5.com/questions/self-ip-address-selection-with-multiple-to-choose-from, I checked the firewall logs again. And now the pieces fit.

     

    On the Virtual Servers I have SNAT Automap enabled. When I only have one floating self IP, that floating self IP is used to initiate traffic to backend servers. When I add more floating self IPs, it will use any of those floating self IPs to initiate traffic towards the backend servers.

     

    The firewall between the F5 and the backend servers does not accept this traffic, meaning not actually the VS stopped responding after I added the VS IP address as a floating self IP, but the firewall blocked traffic towards the backend servers.

     

    So, conclusion (just to summarize):

     

    • only one floating self IP is needed for SNAT communication towards the backend servers (if the amount of connections is less than 65000, otherwise more are needed and I must define a SNAT pool or allow the other floating IP addresses to communicate to the backend servers)
    • I will remove the unneeded floating self IP, since they're not needed for a VS to function as a listener IP

    Thanks all for your help!