Supported Load Balancing Methods

The Loadbalancer.org appliance supports multiple load balancing methods/modes. These can be used at the same time or in combination with each other and are described in the table below.

Layer	Method/Mode	Comments	Topology	Note
4	DR Mode (Direct Routing)	Ultra-fast layer 4 load balancing Requires the "ARP problem" to be solved on each Real Server - for details see DR Mode Considerations	One-Arm (*)	1
4	DNAT Mode (Destination Network Address Translation)	Fast Layer 4 load balancing The appliance must be the default gateway for the Real Servers	One-Arm or Two-Arm	1
4	TUN Mode (Tunneling)	Similar to DR mode but works across IP encapsulated tunnels Requires the "ARP problem" to be solved on each Real Server - for details see DR Mode Considerations	One-Arm	2
4	SNAT Mode (Source Network Address Translation)	Fast layer 4 load balancing Requires no Real Server configuration changes	One-Arm or Two-Arm	3
7	SNAT Mode (Source Network Address Translation)	Not as fast as layer 4 methods, but offers greater flexibility, supports remote server load balancing and advanced functionality such as multiple persistence methods, header manipulation and URL rewriting Based on HAProxy Requires no Real Server configuration changes	One-Arm or Two-Arm	4
7	SSL/TLS Termination	Typically required to enable cookie persistence, header manipulation and URL rewriting in HTTPS streams HAProxy is used as the terminator	One-Arm or Two-Arm	5

(*) DR mode can also be used in a multi-homed configuration where Real Servers are located in different subnets. In this case, the load balancer must have an interface in each subnet to enable layer 2 connectivity which is required for DR mode to operate.

Notes

Recommended for high performance fully transparent and scalable solutions.
Only required for DR mode implementations across routed networks (rarely used).
Useful when you want to load balance both TCP and UDP, but you’re unable to use DR mode or NAT mode due to network topology or Real Server related reasons.
Used across multiple environments including object storage, healthcare and various Microsoft application such as Exchange, IIS and RDS.
SSL/TLS termination is processor intensive - where possible, for a scalable solution terminating on the Real Servers is recommended.

Full details of each mode can be found here.