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Cisco ASA Series CLI Configuration Guide
 
Chapter 1      Configuring Network Object NAT
  Feature History for Network Object NAT
NAT support for reverse DNS lookups 9.0(1) NAT now supports translation of the DNS PTR record for 
reverse DNS lookups when using IPv4 NAT, IPv6 NAT, and 
NAT64 with DNS inspection enabled for the NAT rule.
Per-session PAT 9.0(1) The per-session PAT feature improves the scalability of PAT 
and, for clustering, allows each member unit to own PAT 
connections; multi-session PAT connections have to be 
forwarded to and owned by the master unit. At the end of a 
per-session PAT session, the ASA sends a reset and 
immediately removes the xlate. This reset causes the end 
node to immediately release the connection, avoiding the 
TIME_WAIT state. Multi-session PAT, on the other hand, 
uses the PAT timeout, by default 30 seconds. For 
“hit-and-run” traffic, such as HTTP or HTTPS, the 
per-session feature can dramatically increase the 
connection rate supported by one address. Without the 
per-session feature, the maximum connection rate for one 
address for an IP protocol is approximately 2000 per 
second. With the per-session feature, the connection rate for 
one address for an IP protocol is 65535/average-lifetime.
By default, all TCP traffic and UDP DNS traffic use a 
per-session PAT xlate. For traffic that requires multi-session 
PAT, such as H.323, SIP, or Skinny, you can disable 
per-session PAT by creating a per-session deny rule.
We introduced the following commands: xlate per-session, 
show nat pool.
Table 1-1 Feature History for Network Object NAT (continued)
Feature Name
Platform 
Releases Feature Information