How to allow F5 to do basic routing and allow out of order syn-acks

Hi,

I am pretty new to F5 Load balancers so this might be a very simple question.

I have below setup:

Client --- > LB (VIP) ---> Servers.

• I am not SNATing so the LB retains source IP when sending traffic to the servers.
• But, to ensure that return traffic traverses via LB, I have added a static route on my servers (just for my client IP) to go via LB's interface self IP (IP in the subnet of my nodes/servers).

When I access VIP with this setting, I am not able to load the page completely - which I believe might be something in our application.

But, even if I access the node directly (with static route on servers), LB seems to drop the return traffic. I see SYN-ACKs being RST. (It does not see the SYNs because it probably follows different path).

I have Forwarding IP Virtual server (With FastL4) allowing on all VLANs for any source and any destination.

I am running 15.1.0 version.

Verified that F5 can ping client IP and back-end nodes.. so it knows how to reach back the client.

Any ideas why F5 would block out of order SYN-ACKs? Is there any other obvious configuration that I missed?