What are use cases of this "no-alias" NAT option. All references I found in 
Cisco docs say little to me.

Quoting:

* Autoaliasing of Pool Addresses:
Many customers want to configure the NAT software to translate their local 
addresses to global addresses allocated from unused addresses from an attached 
subnet.
This requires that the router answer ARP requests for those addresses so that 
packets destined for the global addresses are accepted by the router and 
translated.
(Routing takes care of this packet delivery when the global addresses are 
allocated from a virtual network which isn't connected to anything.) When a NAT 
pool used
as an inside global or outside local pool consists of addresses on an attached 
subnet, the software will generate an alias for that address so that the router 
will answer
ARPs for those addresses.

This automatic aliasing also occurs for inside global or outside local 
addresses in static entries. It can be disabled for static entries can be 
disabled by using the "no-alias" keyword:.
ip nat inside source static <local-ip-address> <global-ip-address> no-alias

Why would the router NOT reply on behalf of those global addresses ?

Eugene
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