Cisco Systems and the ASA Services Module Manual De Usuario

 lists each feature change and the platform release in which it was implemented.

Network Object NAT

8.3(1)

Configures NAT for a network object IP address(es).

We introduced or modified the following commands: nat 
(object network configuration mode), show nat, show 
xlate, show nat pool.

Identity NAT configurable proxy ARP and route 
lookup

8.4(2)/8.5(1)

In earlier releases for identity NAT, proxy ARP was 
disabled, and a route lookup was always used to determine 
the egress interface. You could not configure these settings. 
In 8.4(2) and later, the default behavior for identity NAT 
was changed to match the behavior of other static NAT 
configurations: proxy ARP is enabled, and the NAT 
configuration determines the egress interface (if specified) 
by default. You can leave these settings as is, or you can 
enable or disable them discretely. Note that you can now 
also disable proxy ARP for regular static NAT.

When upgrading to 8.4(2) from 8.3(1), 8.3(2), and 8.4(1), 
all identity NAT configurations will now include the 
no-proxy-arp and route-lookup keywords, to maintain 
existing functionality.

We modified the following command: nat static 
[no-proxy-arp] [route-lookup].

PAT pool and round robin address assignment

8.4(2)/8.5(1)

You can now specify a pool of PAT addresses instead of a 
single address. You can also optionally enable round-robin 
assignment of PAT addresses instead of first using all ports 
on a PAT address before using the next address in the pool. 
These features help prevent a large number of connections 
from a single PAT address from appearing to be part of a 
DoS attack and makes configuration of large numbers of 
PAT addresses easy.

We modifed the following command: nat dynamic 
[pat-pool mapped_object [round-robin]].

Round robin PAT pool allocation uses the same 
IP address for existing hosts

8.4(3)

When using a PAT pool with round robin allocation, if a host 
has an existing connection, then subsequent connections 
from that host will use the same PAT IP address if ports are 
available.

We did not modify any commands.