Routing http requests through HAproxy as Load balancer

We have policy url uses the custom url of the appliace and cannot be changed as it uses the appliance fqdn name for the https requests. all client applications and HAproxy load balancer are on same Vlan. We have configured the frountend of the haproxy load balancer IP and backend we have configured the appliance IP and fqdn names with port number.
If we add the Host entry of the actual backend appliance on the client nodes it can reach however since they are in the same VLAN, if we remove and add Virtual IP attached to haproxy load balancer
we shall not be able to reach we get error "unable to resolve host name.
We have the DNS entries for backend servers and also the virtual IP.
Please help