One arm vs. Two arm load balancing.

Two arm - in line mode - Routed mode In this senario the clients and the servers are in 2 different networks (2 arms) and can talk to each other via load balancer which sits between them - inline. Clients are front end, servers are back end with load balancer in between. In most of the cases the backend servers have the load balancer as their gateway and the source or client ip can be preserved.

NOTE - Only the destination IP is changed.

 Single arm - One arm In this mode the load balancer is not in-line, the clients and the servers are in the same network. There is no need for the servers to have load balancer as the gateway. Since we need to load balance the client will talk to the load balancer VIP and the server should be able to send the traffic back to the load balancer...but remember since the servers do not have the load balancers as the gateway we need to use SNAT for the servers to talk back to the LTM or it could cause assymetric routing problem.

NOTE - Both source and destination ip's are changed.