The following are requirements for DSR load balancing:
- Support for DSR on the load balancer. Note: Different vendors may call this feature by different names. Citrix refers to the capability as MAC-based forwarding.
- Load-balanced servers (in this case, service points) must have support for ARP-less IP
addresses.
This is required because if load-balanced service points respond to ARP requests, the load balancer won't know how to distribute load across the service points farm otherwise.
The load balancer distributes traffic to the service points farm using the service points farm’s Layer 2 addresses and the source IP address of the client. IP packets are addressed to the VIP and passed through to the server farm. Therefore, each service point in the farm must be able to respond to the VIP. This is commonly implemented as an IP (the VIP) on the loopback (lo) interface.
- All service points must be on the same Layer 2 network as the load balancer’s private side interface.
- Health checks, configured on the load balancer, that test connectivity to the service points farm should be configured to use the actual (unique) IP address of each service point.
- BlueCat recommends that a DNS test be used as the health check, and that any service point that fails the health check be immediately removed from service.
- You must Configure static network settings on the service points. DSR doesn't work with DHCP-configured service points.