NFS requests from privileged port (< 1024) issues with port-reuse
I have a forwarding virtual server configured with the recommended settings except for increasing the idle timeout due to NFS mounts. The timeout is set to 3600 seconds.
Problem we are seeing in due to NFS port-reuse below 1024. If for any reason there is a network error or the Client Servers loose connection with the NAS filer the sympton is the Client waits 5 minutes then sends a SYN. This SYN uses the same source IP and the same source Port as the original connection. The F5 seeing a SYN coming from a device with the SAME IP and the SAME Source Port will DROP the packet. Until the connection is cleared the systems can no longer communicate. The Client keeps sending the SYN ever 10 seconds which resets the idle timeout so the connection will never drop. The only solution is to re-initialize the Client which then will send the SYN on a different Source Port. This does not happen if the Client uses port above 1024 but that is a security risk due to a non-root user gaining access.
Someone mentioned using TCP Keep-Alives? We have not tried this but any thoughts? If i do clear the connection in the connection table the request immediately goes thru and once again a connection is established.