Deploying Bridge-Path; Direct Server Return - Barracuda Networks Load Balancer Administrator's Manual

Figure 2.4: Sample Bridge-Path network layout

Deploying Bridge-Path

In Bridge-Path mode, the Real Servers must be physically isolated behind the Barracuda Load
Balancer. This means that each Real Server is no longer visible on the network if the Barracuda Load
Balancer becomes unavailable (a separate switch is absolutely required for models 440 and below).
Each Real Server must be one hop away from the LAN port on the Barracuda Load Balancer. This
means their switch must be directly connected into the LAN port of the Barracuda Load Balancer, or
connected to a series of switches that eventually reach the LAN port of the Barracuda Load Balancer
without going through any other machines. The Real Servers must be on the same subnet and logical
network as the Barracuda Load Balancer, the VIPs, and the rest of the WAN, and they must specify
the same gateway as the Barracuda Load Balancer.
Finally, make sure that the Operating Mode of the Barracuda Load Balancer is set to Bridge-Path on
the page. The LAN IP Address on the same page should be empty.
Basic>IP Configuration

Direct Server Return

Direct Server Return (DSR) is an option associated with a Real Server which allows for increased
outbound traffic throughput. In DSR, connection requests and incoming traffic still go from the
Barracuda Load Balancer to the Real Server, but all outgoing traffic goes directly from the Real
Server to the client. Because the Barracuda Load Balancer does not process the outbound traffic, the
throughput is increased.
Because the Barracuda Load Balancer does not process the outgoing traffic, Direct Server Return
does not support SSL offloading or cookie persistence.
With DSR, requests come through the WAN interface of the Barracuda Load Balancer and are handed
off to the Real Servers via the WAN port. The Real Servers then respond directly to the request
22 Barracuda Load Balancer Administrator's Guide