"...
Response packet from F5 to Client => SIP: ??? DIP:1.1.1.1
Instead of "???" which SIP is correct? 192.168.1.1 or 192.168.2.1? I assume and as you said previously (and I want to be) it is 192.168.1.1"
"(https://support.f5.com/kb/en-us/products/big-ip_ltm/manuals/product/ltm-concepts-11-4-0/2.html) 1.1.1.1 is not configured on F5 and maybe VS 0/0 will be chosen. In other hand, this quotation does not say if it applies to first/incoming traffic or return traffic."
- Response packets are already routed back as per connections table records, not as per virtual server configurations. You certainly don't have to configure 1.1.1.1 VS to ensure response packets are routed back.