As pointed on the prevous post, symmetrical traffic is needed for performance and if there is firewall on the ESG. This could be achieved in 2 ways:
1. Using NAT on ESG for the VM and using Global Load Balancer. If Nat pools are kept on seperate subnets, the ingress and egress woiuld be symmetrical. This needs the GLB to understand on which side the Application servers reside and change the dns replies dynamically. If there is no server for App-A on Site-2, it should stop site-2 replies.
2. If NAT is not used, UDLR could understand on which site a VM exists from the arp table, and start to announce this specific /32 host route towards ESG, which in turn announces this route to physical Wan cloud. Thus clients ingress and egress is always symmetrical. If there are 2 vMs with Ips VM-1 10.10.10.10/24 on site-1, and VM-2 10.10.10.20/24 on site-2 ingress and egress is symmetrical, and if VM-1 goes to site-2, the ingress traffic towards VM-1 changes to Site-2. GLB again could distribute the load betweeb sites according to number of App servers for different sites.
For active-standby scenarios GLB could not be needed.