Chapter 7 Defining Signatures

Configuring Signatures

The following options apply:

tcp-3-way-handshake-required [true false]—Specifies that the sensor should only track sessions for which the 3-way handshake is completed. The default is true.

tcp-reassembly-mode—Specifies the mode the sensor should use to reassemble TCP sessions:

strict—Only allows the next expected in the sequence (default).

loose—Allows gaps in the sequence.

asym—Allows asymmetric traffic to be reassembled.

Caution The asymmetric option disables TCP window evasion checking.

Configuring the TCP Stream Reassembly Parameters

To configure the TCP stream reassembly parameters, follow these steps:

Step 1 Log in to the CLI using an account with administrator or operator privileges.

Step 2 Enter TCP stream reassembly submode.

sensor# configure terminal

sensor(config)# service signature-definition sig1

sensor(config-sig)# stream-reassembly

Step 3 Specify that the sensor should only track session for which the 3-way handshake is completed.

sensor(config-sig-str)#tcp-3-way-handshake-required true

Step 4 Specify the mode the sensor should use to reassemble TCP sessions.

sensor(config-sig-str)#tcp-reassembly-mode strict

Step 5 Verify the settings.

sensor(config-sig-str)# show settings stream-reassembly

-----------------------------------------------

tcp-3-way-handshake-required: true default: true

tcp-reassembly-mode: strict default: strict

-----------------------------------------------

sensor(config-sig-str)#

Step 6 Exit signature definition submode.

sensor(config-sig-str)# exit

sensor(config-sig)# exit Apply Changes:?[yes]:

Step 7 Press Enter to apply the changes or enter no to discard them.

For More Information

For information on asymmetric inspection options for sensors configured in inline mode, see Inline TCP Session Tracking Mode, page 5-3and Adding, Editing, and Deleting Virtual Sensors, page 5-4.

 

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Cisco Systems IPS4510K9 Configuring the TCP Stream Reassembly Parameters, Sensorconfig-sig-str#tcp-reassembly-mode strict

IPS4510K9 specifications

Cisco Systems has long been a leading player in network security, and its IPS (Intrusion Prevention System) series is a testament to its commitment to safeguarding digital environments. Among its notable offerings are the IPS4510K9 and IPS4520K9 models, both designed to provide advanced threat protection for mid-sized to large enterprise networks.

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