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Cisco ASA 5500 Series Configuration Guide using the CLI
Chapter43 Configuring Inspection of Basic Internet Protocol s
DNS Inspection
Where the policy_map_name is the name of the policy map. The CLI enters policy-map configuration
mode.
Step5 (Optional) To add a description to the policy map, enter the following command:
hostname(config-pmap)# description string
Step6 To apply actions to matching traffic, perform the following steps.
a. Specify the traffic on which you want to perform actions using one of the following methods:
•Specify the DNS class map that you created in Step3 by entering the following command:
hostname(config-pmap)# class class_map_name
hostname(config-pmap-c)#
•Specify traffic directly in the policy map using one of the match commands described in Step3.
If you use a match not command, then any traffic that does not match the criterion in the match
not command has the action applied.
b. Specify the action you want to perform on the matching traffic by entering the following command:
hostname(config-pmap-c)# {[drop [send-protocol-error] |
drop-connection [send-protocol-error]| mask | reset] [log] | rate-limit message_rate}
Not all options are available for each match or class command. See the CLI help or the command
reference for the exact options available.
The drop keyword drops all packets that match.
The send-protocol-error keyword sends a protocol error message.
The drop-connection keyword drops the packet and closes the connection.
The mask keyword masks out the matching portion of the packet.
The reset keyword drops the packet, closes the connection, and sends a TCP reset to the server
and/or client.
The log keyword, which you can use alone or with one of the other keywords, sends a system log
message.
The rate-limit message_rate argument limits the rate of messages.
You can specify multiple class or match commands in the policy map. For information about the order
of class and match commands, see the “Defining Actions in an Inspection Policy Map” section on
page 33-2.
Step7 To configure parameters that affect the inspection engine, perform the following steps:
a. To enter parameters configuration mode, enter the following command:
hostname(config-pmap)# parameters
hostname(config-pmap-p)#
b. To randomize the DNS identifier for a DNS query, enter the following command:
hostname(config-pmap-p)# id-randomization
c. To enable logging for excessive DNS ID mismatches, enter the following command:
hostname(config-pmap-p)# id-mismatch [count number duration seconds] action log
Where the count string argument specifies the maximum number of mismatch instances before a
system message log is sent. The duration seconds specifies the period, in seconds, to monitor.
d. To require a TSIG resource record to be present, enter the following command: