Cisco ASA 5505 Configuration Manual page 505

Chapter 26 Information About NAT
For example, you have a load balancer at 10.1.2.27; depending on the URL requested, it redirects traffic
to the correct web server. (See
Addresses (Static NAT, One-to-Many)" section on page 27-25
example.)
Figure 26-5
209.165.201.4
Information About Other Mapping Scenarios (Not Recommended)
The adaptive security appliance has the flexibility to allow any kind of static mapping scenario:
one-to-one, one-to-many, but also few-to-many, many-to-few, and many-to-one mappings. These other
mapping options, however, might result in unintended consequences. We recommend using only
one-to-one or one-to-many mappings.
Functionally, few-to-many is the same as one-to-many; but because the configuration is more
complicated, we recommend creating a one-to-many configuration for each real address that requires it.
For example, for a few-to-many scenario, the few real addresses are mapped to the many mapped
addresses in order (A to 1, B to 2, C to 3). When all real addresses are mapped, the next mapped address
is mapped to the first real address, and so on until all mapped addresses are mapped (A to 4, B to 5, C
to 6). This results in multiple mapped addresses for each real address. Just like a one-to-many
configuration, only the first mappings are bidirectional; subsequent mappings allow traffic to be initiated
to the real host, but all traffic from the real host uses only the first mapped address for the source.
OL-20339-01
Figure
One-to-Many Static NAT
Undo Translation
209.165.201.3 10.1.2.27
Undo Translation
10.1.2.27
26-5. See the "Inside Load Balancer with Multiple Mapped
for details on how to configure this
Host
Outside Undo Translation
209.165.201.5
Inside
Load Balancer
10.1.2.27
Web Servers
Cisco ASA 5500 Series Configuration Guide using ASDM
NAT Types
10.1.2.27
26-7