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Cisco Intrusion Prevention System Sensor CLI Configuration Guide for IPS 7.2
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Chapter4 Configuring Interfaces
Configuring Promiscuous Mode
intended target for certain types of attacks, such as atomic attacks (single-packet attacks). The response
actions implemented by promiscuous sensor devices are post-event responses and often require
assistance from other networking devices, for example, routers and firewalls, to respond to an attack.
While such response actions can prevent some classes of attacks, in atomic attacks the single packet has
the chance of reaching the target system before the promiscuous-based sensor can apply an ACL
modification on a managed device (such as a firewall, switch, or router).
By default, all sensing interfaces are in promiscuous mode. To change an interface from inline interface
mode to promiscuous mode, delete any inline interface that contains that interface and delete any inline
VLAN pair subinterfaces of that interface from the interface configuration.
Figure 4-1 illustrates promiscuous mode:
Figure 4-1 Promiscuous Mode
Configuring Promiscuous Mode
By default, all sensing interfaces are in promiscuous mode. To change an interface from inline mode to
promiscuous mode, delete the inline interface that contains that interface from the interface
configuration.
IPv6, Switches, and Lack of VACL Capture
VACLs on Catalyst switches do not have IPv6 support. The most common method for copying traffic to
a sensor configured in promiscuous mode is to use VACL capture. If you want to have IPv6 support, you
can use SPAN ports.
However, you can only configure up to two monitor sessions on a switch unless you use the following
configuration:
Monitor session
Multiple trunks to one or more sensors
Restrict per trunk port which VLANs are allowed to perform monitoring of many VLANs to m ore
than two different sensors or virtual sensors within one IPS
Router Host
Sensor
Switch
Span port sending
copies of VLAN A traffic
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VLAN A