Cisco Cisco Email Security Appliance C170 Guia Do Utilizador

Beginning with the 3.8.3 release of AsyncOS, you can track and rate limit 
incoming mail on a per-IP address basis while managing sender group entries in 
a listener’s Host Access Table (HAT) in large CIDR blocks. For example, if an 
incoming connection matched against the host “10.1.1.0/24,” a counter could still 
be generated for each individual address within that range, rather than aggregating 
all traffic into one large counter.

In order for the significant bits HAT policy option to take effect, you must not 
enable “User SenderBase” in the Flow Control options for the HAT (or, for the 
CLI, answer 

 to the question for enabling the SenderBase Information Service 

in the 

listenerconfig

 -> setup command: “Would you like to enable SenderBase 

Reputation Filters and IP Profiling support?”). That is, the Hat Significant Bits 
feature and enabling SenderBase IP Profiling support are mutually exclusive. 

In most cases, you can use this feature to define sender groups broadly — that is, 
large groups of IP addresses such as “10.1.1.0/24” or “10.1.0.0/16” — while 
applying mail flow rate limiting narrowly to smaller groups of IP addresses. 

The HAT Significant Bits feature corresponds to these components of the system:

There are two parts of HAT configuration: sender groups and mail flow policies. 
Sender group configuration defines how a sender's IP address is “classified” (put 
in a sender group). Mail flow policy configuration defines how the SMTP session 
from that IP address is controlled. When using this feature, an IP address may be 
“classified in a CIDR block” (e.g. 10.1.1.0/24) sender group while being 
controlled as an individual host (/32). This is done via the “signficant_bits” policy 
configuration setting.