Operating Modes - Cisco ASA Series Cli Configuration Manual

Chapter 1 Configuring the ASA IPS Module

Operating Modes

You can send traffic to the ASA IPS module using one of the following modes:
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Figure 1-2
Using Virtual Sensors (ASA 5510 and Higher)
The ASA IPS module running IPS software Version 6.0 and later can run multiple virtual sensors, which
means you can configure multiple security policies on the ASA IPS module. You can assign each ASA
security context or single mode ASA to one or more virtual sensors, or you can assign multiple security
contexts to the same virtual sensor. See the IPS documentation for more information about virtual
sensors, including the maximum number of sensors supported.
Figure 1-3
contexts share the same virtual sensor.
Inline mode—This mode places the ASA IPS module directly in the traffic flow (see
No traffic that you identified for IPS inspection can continue through the ASA without first passing
through, and being inspected by, the ASA IPS module. This mode is the most secure because every
packet that you identify for inspection is analyzed before being allowed through. Also, the ASA IPS
module can implement a blocking policy on a packet-by-packet basis. This mode, however, can
affect throughput.
Promiscuous mode—This mode sends a duplicate stream of traffic to the ASA IPS module. This
mode is less secure, but has little impact on traffic throughput. Unlike inline mode, in promiscuous
mode the ASA IPS module can only block traffic by instructing the ASA to shun the traffic or by
resetting a connection on the ASA. Also, while the ASA IPS module is analyzing the traffic, a small
amount of traffic might pass through the ASA before the ASA IPS module can shun it.
shows the ASA IPS module in promiscuous mode. In this example, the ASA IPS module sends a
shun message to the ASA for traffic it identified as a threat.
ASA IPS module Traffic Flow in the ASA: Promiscuous Mode
Main System
inside
Shun
message
Copied Traffic
IPS inspection
IPS
shows one security context paired with one virtual sensor (in inline mode), while two security
ASA
VPN
Firewall
Decryption
Policy outside
Cisco ASA Series CLI Configuration Guide
Information About the ASA IPS module
Figure
Figure 1-2
1-1).
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