How to do a load balance dual ISP on Cisco ASA?

If user has two ISPs terminating on the ASA, the ASA is configured for ISP redundancy. So in some cases users would like to use both ISP to send the traffic outside. In such scenarios the best solution would be to use the Router. Using route-map on the router, one can confgure routing in such a way that certain kinds of uses one ISP while the second ISP is used for other type of traffic. Even though ASA supports route-maps it is not designed to perform extensive routing capabilities.

The ASA can be used to load balance traffic based on destination ip address
Using the following command we can route traffic to half the destinations on the internet using ISP1 and the other half using ISP2:


nat (inside) 1 0 0

global (outside-ISP1) 1 interface

global (outside-ISP2) 1 interface

creates a default route for addresses in the first half of the IPv4 spectrum

route outside-ISP1 128.0.0.0 128.0.0.0 1.1.1.2

creates a default route for addresses in the second half of the IPv4 sepctrum

route outside-ISP2 0.0.0.0 128.0.0.0 2.2.2.2


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