Hi,
This is for inbound connection.
below is the scenario.
1. ISP --- > inbound traffic -- > FW (incoming interface 1 and exit interface 2) --- > Load balancer --- > backend servers.
2. Same ISP -- > inbound traffic -- > FW (same firewall - incoming interface 1 and exit interface 5 ) -- > Load balancer(same LB) -- > backend servers.
problem is already we have a default route pointing towards firewall interface 2 from load balancer.
having one more default towards different different interface is not feasible.
hence inbound public ip is natted, nat ip reaches LB, where LB has the comfort of routing nat'd ip towards different interface.