D-Link DFL-210 - NetDefend - Security Appliance, User Manual

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4.4. Route Load Balancing
Overview
NetDefendOS provides the option to perform Route Load Balancing (RLB). This is the ability to
distribute traffic over multiple alternate routes based on a number of predefined distribution
algorithms.
The purpose of this feature is to provide the following:
• Balancing of traffic between interfaces in a policy driven fashion.
• To balance simultaneous utilization of multiple Internet links so networks are not dependent on
a single ISP.
• To allow balancing of traffic across multiple VPN tunnels which might be setup over different
physical interfaces.
Enabling RLB
RLB is enabled on a routing table basis and this is done by creating an RLB Instance object. This
object specifies two parameters: a routing table and an RLB algorithm. A table may have only one
Instance object associated with it.
One of the algorithms from the following list can be specified in an RLB Instance object:
• Round Robin
Matching routes are used equally often by successively going to the next matching route.
• Destination
This is an algorithm that is similar to Round Robin but provides destination IP "stickiness" so
that the same destination IP address gets the same route.
• Spillover
This uses the next route when specified interface traffic limits are exceeded continuously for a
given time.
Disabling RLB
Deleting a routing table's Instance object has the effect of switching off RLB for that table.
RLB Operation
When RLB is enabled for a routing table through an RLB Instance object, the sequence of
processing steps is as follows:
1. Route lookup is done in the routing table and a list of all matching routes is assembled. The
routes in the list must cover the exact same IP address range (further explanation of this
requirement can be found below).
2. If the route lookup finds only one matching route then that route is used and balancing does not
take place.
4.4. Route Load Balancing Chapter 4. Routing
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