Cisco Security Appliance Command Line Configuration Guide, Version 8.0 - Using Modular Policy Framework [Cisco ASA 5500 Series Adaptive Security Appliances]

Table Of Contents

Using Modular Policy Framework

Modular Policy Framework Overview

Default Global Policy

Identifying Traffic Using a Layer 3/4 Class Map

Creating a Layer 3/4 Class Map for Through Traffic

Creating a Layer 3/4 Class Map for Management Traffic

Configuring Special Actions for Application Inspections

Creating a Regular Expression

Creating a Regular Expression Class Map

Identifying Traffic in an Inspection Class Map

Defining Actions in an Inspection Policy Map

Defining Actions Using a Layer 3/4 Policy Map

Layer 3/4 Policy Map Overview

Policy Map Guidelines

Supported Feature Types

Feature Directionality

Feature Matching Guidelines within a Policy Map

Feature Matching Guidelines for multiple Policy Maps

Order in Which Multiple Feature Actions are Applied

Default Layer 3/4 Policy Map

Adding a Layer 3/4 Policy Map

Applying a Layer 3/4 Policy to an Interface Using a Service Policy

Modular Policy Framework Examples

Applying Inspection and QoS Policing to HTTP Traffic

Applying Inspection to HTTP Traffic Globally

Applying Inspection and Connection Limits to HTTP Traffic to Specific Servers

Applying Inspection to HTTP Traffic with NAT

Using Modular Policy Framework

This chapter describes how to use Modular Policy Framework to create security policies for TCP and general connection settings, inspections, IPS, CSC, and QoS.

This chapter includes the following sections:

•Modular Policy Framework Overview

•Identifying Traffic Using a Layer 3/4 Class Map

•Configuring Special Actions for Application Inspections

•Defining Actions Using a Layer 3/4 Policy Map

•Applying a Layer 3/4 Policy to an Interface Using a Service Policy

•Modular Policy Framework Examples

Modular Policy Framework Overview

Modular Policy Framework provides a consistent and flexible way to configure security appliance features. For example, you can use Modular Policy Framework to create a timeout configuration that is specific to a particular TCP application, as opposed to one that applies to all TCP applications.

Modular Policy Framework supports the following features:

•TCP normalization, TCP and UDP connection limits and timeouts, and TCP sequence number randomization

•CSC

•Application inspection

•IPS

•QoS input policing

•QoS output policing

•QoS priority queue

Configuring Modular Policy Framework consists of four tasks:

1. Identify the Layer 3 and 4 traffic to which you want to apply actions. See the "Identifying Traffic Using a Layer 3/4 Class Map" section.

2. (Application inspection only) Define special actions for application inspection traffic. See the "Configuring Special Actions for Application Inspections" section.

3. Apply actions to the Layer 3 and 4 traffic. See the "Defining Actions Using a Layer 3/4 Policy Map" section.

4. Activate the actions on an interface. See the "Applying a Layer 3/4 Policy to an Interface Using a Service Policy" section.

Default Global Policy

By default, the configuration includes a policy that matches all default application inspection traffic and applies certain inspections to the traffic on all interfaces (a global policy). Not all inspections are enabled by default. You can only apply one global policy, so if you want to alter the global policy, you need to either edit the default policy or disable it and apply a new one. (An interface policy overrides the global policy.)

The default policy configuration includes the following commands:
class-map inspection_default
 match default-inspection-traffic
policy-map type inspect dns preset_dns_map
 parameters
  message-length maximum 512
policy-map global_policy
 class inspection_default
  inspect dns preset_dns_map 
  inspect ftp 
  inspect h323 h225 
  inspect h323 ras 
  inspect rsh 
  inspect rtsp 
  inspect esmtp 
  inspect sqlnet 
  inspect skinny 
  inspect sunrpc 
  inspect xdmcp 
  inspect sip 
  inspect netbios 
  inspect tftp 
service-policy global_policy global
Identifying Traffic Using a Layer 3/4 Class Map

A Layer 3/4 class map identifies Layer 3 and 4 traffic to which you want to apply actions. The maximum number of Layer 3/4 class maps is 255 in single mode or per context in multiple mode. The configuration includes a default Layer 3/4 class map that the security appliance uses in the default global policy. It is called inspection_default and matches the default inspection traffic:
class-map inspection_default
 match default-inspection-traffic
You can create multiple Layer 3/4 class maps for each Layer 3/4 policy map. You can create the following types of class maps:

•Creating a Layer 3/4 Class Map for Through Traffic

•Creating a Layer 3/4 Class Map for Management Traffic

Creating a Layer 3/4 Class Map for Through Traffic

A Layer 3/4 class map matches traffic based on protocols, ports, IP addresses and other Layer 3 or 4 attributes.

To define a Layer 3/4 class map, perform the following steps:

Step 1 Create a Layer 3/4 class map by entering the following command:
hostname(config)# class-map class_map_name
hostname(config-cmap)# 
Where class_map_name is a string up to 40 characters in length. The name "class-default" is reserved. All types of class maps use the same name space, so you cannot reuse a name already used by another type of class map. The CLI enters class-map configuration mode.

Step 2 (Optional) Add a description to the class map by entering the following command:
hostname(config-cmap)# description string
Step 3 Define the traffic to include in the class by matching one of the following characteristics. Unless otherwise specified, you can include only one match command in the class map.

•Any traffic—The class map matches all traffic.
hostname(config-cmap)# match any
•Access list—The class map matches traffic specified by an extended access list. If the security appliance is operating in transparent firewall mode, you can use an EtherType access list.
hostname(config-cmap)# match access-list access_list_name
For more information about creating access lists, see the "Adding an Extended Access List" section on page 16-5 or the "Adding an EtherType Access List" section on page 16-8.

For information about creating access lists with NAT, see the "IP Addresses Used for Access Lists When You Use NAT" section on page 16-3.

•TCP or UDP destination ports—The class map matches a single port or a contiguous range of ports.
hostname(config-cmap)# match port {tcp | udp} {eq port_num | range port_num port_num}
Tip For applications that use multiple, non-contiguous ports, use the match access-list command and define an ACE to match each port.

For a list of ports you can specify, see the "TCP and UDP Ports" section on page D-11.

For example, enter the following command to match TCP packets on port 80 (HTTP):
hostname(config-cmap)# match tcp eq 80
•Default traffic for inspection—The class map matches the default TCP and UDP ports used by all applications that the security appliance can inspect.
hostname(config-cmap)# match default-inspection-traffic
See the "Default Inspection Policy" section on page 25-3 for a list of default ports. The security appliance includes a default global policy that matches the default inspection traffic, and applies common inspections to the traffic on all interfaces. Not all applications whose ports are included in the match default-inspection-traffic command are enabled by default in the policy map.

You can specify a match access-list command along with the match default-inspection-traffic command to narrow the matched traffic. Because the match default-inspection-traffic command specifies the ports to match, any ports in the access list are ignored.

•DSCP value in an IP header—The class map matches up to eight DSCP values.
hostname(config-cmap)# match dscp value1 [value2] [...] [value8]
For example, enter the following:
hostname(config-cmap)# match dscp af43 cs1 ef
•Precedence—The class map matches up to four precedence values, represented by the TOS byte in the IP header.
hostname(config-cmap)# match precedence value1 [value2] [value3] [value4]
where value1 through value4 can be 0 to 7, corresponding to the possible precedences.

•RTP traffic—The class map matches RTP traffic.
hostname(config-cmap)# match rtp starting_port range
The starting_port specifies an even-numbered UDP destination port between 2000 and 65534. The range specifies the number of additional UDP ports to match above the starting_port, between 0 and 16383.

•Tunnel group traffic—The class map matches traffic for a tunnel group to which you want to apply QoS.
hostname(config-cmap)# match tunnel-group name
You can also specify one other match command to refine the traffic match. You can specify any of the preceding commands, except for the match any, match access-list, or match default-inspection-traffic commands. Or you can enter the following command to police each flow:
hostname(config-cmap)# match flow ip destination address
All traffic going to a unique IP destination address is considered a flow.

The following is an example for the class-map command:
hostname(config)# access-list udp permit udp any any
hostname(config)# access-list tcp permit tcp any any
hostname(config)# access-list host_foo permit ip any 10.1.1.1 255.255.255.255
hostname(config)# class-map all_udp
hostname(config-cmap)# description "This class-map matches all UDP traffic"
hostname(config-cmap)# match access-list udp
hostname(config-cmap)# class-map all_tcp
hostname(config-cmap)# description "This class-map matches all TCP traffic"
hostname(config-cmap)# match access-list tcp
hostname(config-cmap)# class-map all_http
hostname(config-cmap)# description "This class-map matches all HTTP traffic"
hostname(config-cmap)# match port tcp eq http
hostname(config-cmap)# class-map to_server
hostname(config-cmap)# description "This class-map matches all traffic to server 10.1.1.1"
hostname(config-cmap)# match access-list host_foo
Creating a Layer 3/4 Class Map for Management Traffic

For management traffic to the security appliance, you might want to perform actions specific to this kind of traffic. You can specify a management class map that can match an access list or TCP or UDP ports. The types of actions available for a management class map in the policy map are specialized for management traffic. Namely, this type of class map lets you inspect RADIUS accounting traffic and set connection limits.

To create a class map for management traffic to the security appliance, perform the following steps:

Step 1 Create a class map by entering the following command:
hostname(config)# class-map type management class_map_name
hostname(config-cmap)# 
Where class_map_name is a string up to 40 characters in length. The name "class-default" is reserved. All types of class maps use the same name space, so you cannot reuse a name already used by another type of class map. The CLI enters class-map configuration mode.

Step 2 (Optional) Add a description to the class map by entering the following command:
hostname(config-cmap)# description string
Step 3 Define the traffic to include in the class by matching one of the following characteristics. You can include only one match command in the class map.

•Access list—The class map matches traffic specified by an extended access list. If the security appliance is operating in transparent firewall mode, you can use an EtherType access list.
hostname(config-cmap)# match access-list access_list_name
For more information about creating access lists, see the "Adding an Extended Access List" section on page 16-5 or the "Adding an EtherType Access List" section on page 16-8.

For information about creating access lists with NAT, see the "IP Addresses Used for Access Lists When You Use NAT" section on page 16-3.

•TCP or UDP destination ports—The class map matches a single port or a contiguous range of ports.
hostname(config-cmap)# match port {tcp | udp} {eq port_num | range port_num port_num}
Tip For applications that use multiple, non-contiguous ports, use the match access-list command and define an ACE to match each port.

For a list of ports you can specify, see the "TCP and UDP Ports" section on page D-11.

For example, enter the following command to match TCP packets on port 80 (HTTP):
hostname(config-cmap)# match tcp eq 80
Configuring Special Actions for Application Inspections

Modular Policy Framework lets you configure special actions for many application inspections. When you enable an inspection engine in the Layer 3/4 policy map, you can also optionally enable actions as defined in an inspection policy map.

See the "Configuring Application Inspection" section on page 25-5 for a list of applications that support inspection policy maps.

An inspection policy map consists of one or more of the following elements. The exact options available for an inspection policy map depends on the application.

•Traffic matching command—You can define a traffic matching command directly in the inspection policy map to match application traffic to criteria specific to the application, such as a URL string, for which you then enable actions.

•Inspection class map—(Not available for all applications. See the CLI help for a list of supported applications.) An inspection class map includes traffic matching commands that match application traffic with criteria specific to the application, such as a URL string. You then identify the class map in the policy map and enable actions. The difference between creating a class map and defining the traffic match directly in the inspection policy map is that you can create more complex match criteria and you can reuse class maps.

•Parameters—Parameters affect the behavior of the inspection engine.

Some traffic matching commands can specify regular expressions to match text inside a packet. Be sure to create and test the regular expressions before you configure the policy map, either singly or grouped together in a regular expression class map.

The default inspection policy map configuration includes the following commands, which sets the maximum message length for DNS packets to be 512 bytes:
policy-map type inspect dns preset_dns_map
 parameters
  message-length maximum 512
Note There are other default inspection policy maps such as policy-map type inspect esmtp _default_esmtp_map. These default policy maps are created implicitly by the command inspect protocol. For example, inspect esmtp implicitly uses the policy map "_default_esmtp_map." All the default policy maps can be shown by using the show running-config all policy-map command.

This section describes how to create additional inspection policy maps, and includes the following topics:

•Creating a Regular Expression

•Creating a Regular Expression Class Map

•Identifying Traffic in an Inspection Class Map

•Defining Actions in an Inspection Policy Map

Creating a Regular Expression

A regular expression matches text strings either literally as an exact string, or by using metacharacters so you can match multiple variants of a text string. You can use a regular expression to match the content of certain application traffic; for example, you can match a URL string inside an HTTP packet.

Use Ctrl+V to escape all of the special characters in the CLI, such as question mark (?) or a tab. For example, type d[Ctrl+V]g to enter d?g in the configuration.

See the regex command in the Cisco Security Appliance Command Reference for performance impact information when matching a regular expression to packets.

Note As an optimization, the security appliance searches on the deobfuscated URL. Deobfuscation compresses multiple forward slashes (/) into a single slash. For strings that commonly use double slashes, like "http://", be sure to search for "http:/" instead.

Table 21-1 lists the metacharacters that have special meanings.

Table 21-1 regex Metacharacters

Character

Description

Notes

.

Dot

Matches any single character. For example, d.g matches dog, dag, dtg, and any word that contains those characters, such as doggonnit.

(exp)

Subexpression

A subexpression segregates characters from surrounding characters, so that you can use other metacharacters on the subexpression. For example, d(o|a)g matches dog and dag, but do|ag matches do and ag. A subexpression can also be used with repeat quantifiers to differentiate the characters meant for repetition. For example, ab(xy){3}z matches abxyxyxyz.

|

Alternation

Matches either expression it separates. For example, dog|cat matches dog or cat.

?

Question mark

A quantifier that indicates that there are 0 or 1 of the previous expression. For example, lo?se matches lse or lose.

Note You must enter Ctrl+V and then the question mark or else the help function is invoked.

*

Asterisk

A quantifier that indicates that there are 0, 1 or any number of the previous expression. For example, lo*se matches lse, lose, loose, and so on.

+

Plus

A quantifier that indicates that there is at least 1 of the previous expression. For example, lo+se matches lose and loose, but not lse.

{x} or {x,}

Minimum repeat quantifier

Repeat at least x times. For example, ab(xy){2,}z matches abxyxyz, abxyxyxyz, and so on.

[abc]

Character class

Matches any character in the brackets. For example, [abc] matches a, b, or c.

[^abc]

Negated character class

Matches a single character that is not contained within the brackets. For example, [^abc] matches any character other than a, b, or c. [^A-Z] matches any single character that is not an uppercase letter.

[a-c]

Character range class

Matches any character in the range. [a-z] matches any lowercase letter. You can mix characters and ranges: [abcq-z] matches a, b, c, q, r, s, t, u, v, w, x, y, z, and so does [a-cq-z].

The dash (-) character is literal only if it is the last or the first character within the brackets: [abc-] or [-abc].

""

Quotation marks

Preserves trailing or leading spaces in the string. For example, " test" preserves the leading space when it looks for a match.

^

Caret

Specifies the beginning of a line.

\

Escape character

When used with a metacharacter, matches a literal character. For example, \[ matches the left square bracket.

char

Character

When character is not a metacharacter, matches the literal character.

\r

Carriage return

Matches a carriage return 0x0d.

\n

Newline

Matches a new line 0x0a.

\t

Tab

Matches a tab 0x09.

\f

Formfeed

Matches a form feed 0x0c.

\xNN

Escaped hexadecimal number

Matches an ASCII character using hexadecimal (exactly two digits).

\NNN

Escaped octal number

Matches an ASCII character as octal (exactly three digits). For example, the character 040 represents a space.

To test and create a regular expression, perform the following steps:

Step 1 To test a regular expression to make sure it matches what you think it will match, enter the following command:
hostname(config)# test regex input_text regular_expression
Where the input_text argument is a string you want to match using the regular expression, up to 201 characters in length.

The regular_expression argument can be up to 100 characters in length.

Use Ctrl+V to escape all of the special characters in the CLI. For example, to enter a tab in the input text in the test regex command, you must enter test regex "test[Ctrl+V Tab]" "test\t".

If the regular expression matches the input text, you see the following message:
INFO: Regular expression match succeeded.
If the regular expression does not match the input text, you see the following message:
INFO: Regular expression match failed.
Step 2 To add a regular expression after you tested it, enter the following command:
hostname(config)# regex name regular_expression
Where the name argument can be up to 40 characters in length.

The regular_expression argument can be up to 100 characters in length.

The following example creates two regular expressions for use in an inspection policy map:
hostname(config)# regex url_example example\.com
hostname(config)# regex url_example2 example2\.com
Creating a Regular Expression Class Map

A regular expression class map identifies one or more regular expressions. You can use a regular expression class map to match the content of certain traffic; for example, you can match URL strings inside HTTP packets.

To create a regular expression class map, perform the following steps:

Step 1 Create one or more regular expressions according to the "Creating a Regular Expression" section.

Step 2 Create a class map by entering the following command:
hostname(config)# class-map type regex match-any class_map_name
hostname(config-cmap)# 
Where class_map_name is a string up to 40 characters in length. The name "class-default" is reserved. All types of class maps use the same name space, so you cannot reuse a name already used by another type of class map.

The match-any keyword specifies that the traffic matches the class map if it matches at least one of the regular expressions.

The CLI enters class-map configuration mode.

Step 3 (Optional) Add a description to the class map by entering the following command:
hostname(config-cmap)# description string
Step 4 Identify the regular expressions you want to include by entering the following command for each regular expression:
hostname(config-cmap)# match regex regex_name
The following example creates two regular expressions, and adds them to a regular expression class map. Traffic matches the class map if it includes the string "example.com" or "example2.com."
hostname(config)# regex url_example example\.com
hostname(config)# regex url_example2 example2\.com
hostname(config)# class-map type regex match-any URLs
hostname(config-cmap)# match regex url_example
hostname(config-cmap)# match regex url_example2
Identifying Traffic in an Inspection Class Map

This type of class map allows you to match criteria that is specific to an application. For example, for DNS traffic, you can match the domain name in a DNS query.

Note Not all applications support inspection class maps. See the CLI help for a list of supported applications.

A class map groups multiple traffic matches (in a match-all class map), or lets you match any of a list of matches (in a match-any class map). The difference between creating a class map and defining the traffic match directly in the inspection policy map is that the class map lets you group multiple match commands, and you can reuse class maps. For the traffic that you identify in this class map, you can specify actions such as dropping, resetting, and/or logging the connection in the inspection policy map. If you want to perform different actions on different types of traffic, you should identify the traffic directly in the policy map.

To define an inspection class map, perform the following steps:

Step 1 Create a class map by entering the following command:
hostname(config)# class-map type inspect application [match-all | match-any] 
class_map_name
hostname(config-cmap)# 
Where the application is the application you want to inspect. For supported applications, see the CLI help for a list of supported applications or see Chapter 25, "Configuring Application Layer Protocol Inspection."

The class_map_name argument is the name of the class map up to 40 characters in length.

The match-all keyword is the default, and specifies that traffic must match all criteria to match the class map.

The match-any keyword specifies that the traffic matches the class map if it matches at least one of the criteria.

The CLI enters class-map configuration mode, where you can enter one or more match commands.

Step 2 (Optional) To add a description to the class map, enter the following command:
hostname(config-cmap)# description string
Step 3 Define the traffic to include in the class by entering one or more match commands available for your application.

To specify traffic that should not match the class map, use the match not command. For example, if the match not command specifies the string "example.com," then any traffic that includes "example.com" does not match the class map.

To see the match commands available for each application, see Chapter 25, "Configuring Application Layer Protocol Inspection."

The following example creates an HTTP class map that must match all criteria:
hostname(config-cmap)# class-map type inspect http match-all http-traffic
hostname(config-cmap)# match req-resp content-type mismatch
hostname(config-cmap)# match request body length gt 1000
hostname(config-cmap)# match not request uri regex class URLs
The following example creates an HTTP class map that can match any of the criteria:
hostname(config-cmap)# class-map type inspect http match-any monitor-http
hostname(config-cmap)# match request method get
hostname(config-cmap)# match request method put
hostname(config-cmap)# match request method post
Defining Actions in an Inspection Policy Map

When you enable an inspection engine in the Layer 3/4 policy map, you can also optionally enable actions as defined in an inspection policy map.

To create an inspection policy map, perform the following steps:

Step 1 To create the HTTP inspection policy map, enter the following command:
hostname(config)# policy-map type inspect application policy_map_name
hostname(config-pmap)# 
See the "Configuring Application Inspection" section on page 25-5 for a list of applications that support inspection policy maps.

The policy_map_name argument is the name of the policy map up to 40 characters in length. All types of policy maps use the same name space, so you cannot reuse a name already used by another type of policy map. The CLI enters policy-map configuration mode.

Step 2 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 inspection class map that you created in the "Identifying Traffic in an Inspection Class Map" section by entering the following command:
hostname(config-pmap)# class class_map_name
hostname(config-pmap-c)# 
Not all applications support inspection class maps.

•Specify traffic directly in the policy map using one of the match commands described for each application in Chapter 25, "Configuring Application Layer Protocol Inspection." If you use a match not command, then any traffic that matches the criterion in the match not command does not have 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 application. Other actions specific to the application might also be available. See Chapter 25, "Configuring Application Layer Protocol Inspection," 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.

If a packet matches multiple different match or class commands, then the order in which the security appliance applies the actions is determined by internal security appliance rules, and not by the order they are added to the policy map. The internal rules are determined by the application type and the logical progression of parsing a packet, and are not user-configurable. For example for HTTP traffic, parsing a Request Method field precedes parsing the Header Host Length field; an action for the Request Method field occurs before the action for the Header Host Length field. For example, the following match commands can be entered in any order, but the match request method get command is matched first.
match request header host length gt 100
  reset
match request method get
  log
If an action drops a packet, then no further actions are performed in the inspection policy map. For example, if the first action is to reset the connection, then it will never match any further match or class commands. If the first action is to log the packet, then a second action, such as resetting the connection, can occur. (You can configure both the reset (or drop-connection, and so on.) and the log action for the same match or class command, in which case the packet is logged before it is reset for a given match.)

If a packet matches multiple match or class commands that are the same, then they are matched in the order they appear in the policy map. For example, for a packet with the header length of 1001, it will match the first command below, and be logged, and then will match the second command and be reset. If you reverse the order of the two match commands, then the packet will be dropped and the connection reset before it can match the second match command; it will never be logged.
match request header length gt 100
  log
match request header length gt 1000
  reset
A class map is determined to be the same type as another class map or match command based on the lowest priority match command in the class map (the priority is based on the internal rules). If a class map has the same type of lowest priority match command as another class map, then the class maps are matched according to the order they are added to the policy map. If the lowest priority command for each class map is different, then the class map with the higher priority match command is matched first. For example, the following three class maps contain two types of match commands: match request-cmd (higher priority) and match filename (lower priority). The ftp3 class map includes both commands, but it is ranked according to the lowest priority command, match filename. The ftp1 class map includes the highest priority command, so it is matched first, regardless of the order in the policy map. The ftp3 class map is ranked as being of the same priority as the ftp2 class map, which also contains the match filename command. They are matched according to the order in the policy map: ftp3 and then ftp2.
class-map inspect type ftp match-all ftp1
  match request-cmd get
class-map inspect type ftp match-all ftp2
  match filename regex abc
class-map inspect type ftp match-all ftp3
  match request-cmd get
  match filename regex abc
policy-map type inspect ftp ftp
  class ftp3
    log
  class ftp2
    log
  class ftp1
    log
Step 3 To configure parameters that affect the inspection engine, enter the following command:
hostname(config-pmap)# parameters
hostname(config-pmap-p)# 
The CLI enters parameters configuration mode. For the parameters available for each application, see Chapter 25, "Configuring Application Layer Protocol Inspection."

The following is an example of an HTTP inspection policy map and the related class maps. This policy map is activated by the Layer 3/4 policy map, which is enabled by the service policy.
hostname(config)# regex url_example example.com
hostname(config)# regex url_example2 example2.com
hostname(config)# class-map type regex match-any URLs
hostname(config-cmap)# match regex url_example
hostname(config-cmap)# match regex url_example2
hostname(config-cmap)# class-map type inspect http match-all http-traffic
hostname(config-cmap)# match req-resp content-type mismatch
hostname(config-cmap)# match request body length gt 1000
hostname(config-cmap)# match not request uri regex class URLs
hostname(config-cmap)# policy-map type inspect http http-map1
hostname(config-pmap)# class http-traffic
hostname(config-pmap-c)# drop-connection log
hostname(config-pmap-c)# match req-resp content-type mismatch
hostname(config-pmap-c)# reset log
hostname(config-pmap-c)# parameters
hostname(config-pmap-p)# protocol-violation action log
hostname(config-pmap-p)# policy-map test
hostname(config-pmap)# class test (a Layer 3/4 class map not shown)
hostname(config-pmap-c)# inspect http http-map1
hostname(config-pmap-c)# service-policy test interface outside
Defining Actions Using a Layer 3/4 Policy Map

This section describes how to associate actions with Layer 3/4 class maps by creating a Layer 3/4 policy map. This section includes the following topics:

•Layer 3/4 Policy Map Overview

•Default Layer 3/4 Policy Map

•Adding a Layer 3/4 Policy Map

Layer 3/4 Policy Map Overview

This section describes how Layer 3/4 policy maps work, and includes the following topics:

•Policy Map Guidelines

•Supported Feature Types

•Feature Directionality

•Feature Matching Guidelines within a Policy Map

•Feature Matching Guidelines for multiple Policy Maps

•Order in Which Multiple Feature Actions are Applied

Policy Map Guidelines

See the following guidelines for using policy maps:

•You can only assign one policy map per interface.

•You can apply the same policy map to multiple interfaces.

•You can identify multiple Layer 3/4 class maps in a Layer 3/4 policy map.

•For each class map, you can assign multiple actions from one or more feature types.

Supported Feature Types

Feature types supported by the Modular Policy Framework that you can enable in the policy map include the following:

•TCP normalization, TCP and UDP connection limits and timeouts, and TCP sequence number randomization

•CSC

•Application inspection

•IPS

•QoS input policing

•QoS output policing

•QoS priority queue

Feature Directionality

Actions are applied to traffic bidirectionally or unidirectionally depending on the feature. For features that are applied bidirectionally, all traffic that enters or exits the interface to which you apply the policy map is affected if the traffic matches the class map for both directions.

Note When you use a global policy, all features are unidirectional; features that are normally bidirectional when applied to a single interface only apply to the ingress of each interface when applied globally. Because the policy is applied to all interfaces, the policy will be applied in both directions so bidirectionality in this case is redundant.

For features that are applied unidirectionally, for example QoS priority queue, only traffic that exits the interface to which you apply the policy map is affected. See Table 21-2 for the directionality of each feature.

Table 21-2 Feature Directionality

Feature

Single Interface Direction

Global Direction

TCP normalization, TCP and UDP connection limits and timeouts, and TCP sequence number randomization

Bidirectional

Ingress

CSC

Bidirectional

Ingress

Application inspection

Bidirectional

Ingress

IPS

Bidirectional

Ingress

QoS input policing

Ingress

Ingress

QoS output policing

Egress

Egress

QoS priority queue

Egress

Egress

Feature Matching Guidelines within a Policy Map

See the following guidelines for how a packet matches class maps in a policy map:

•A packet can match only one class map in the policy map for each feature type.

•When the packet matches a class map for a feature type, the security appliance does not attempt to match it to any subsequent class maps for that feature type.

•If the packet matches a subsequent class map for a different feature type, however, then the security appliance also applies the actions for the subsequent class map.

For example, if a packet matches a class map for connection limits, and also matches a class map for application inspection, then both class map actions are applied.

If a packet matches a class map for application inspection, but also matches another class map that includes application inspection, then the second class map actions are not applied.

Feature Matching Guidelines for multiple Policy Maps

For TCP and UDP traffic (and ICMP when you enable stateful ICMP inspection), Modular Policy Framework operates on traffic flows, and not just individual packets. If traffic is part of an existing connection that matches a feature in a policy on one interface, that traffic flow cannot also match the same feature in a policy on another interface; only the first policy is used.

For example, if HTTP traffic matches a policy on the inside interface to inspect HTTP traffic, and you have a separate policy on the outside interface for HTTP inspection, then that traffic is not also inspected on the egress of the outside interface. Similarly, the return traffic for that connection will not be inspected by the ingress policy of the outside interface, nor by the egress policy of the inside interface.

For traffic that is not treated as a flow, for example ICMP when you do not enable stateful ICMP inspection, returning traffic can match a different policy map on the returning interface. For example, if you configure IPS inspection on the inside and outside interfaces, but the inside policy uses virtual sensor 1 while the outside policy uses virtual sensor 2, then a non-stateful Ping will match virtual sensor 1 outbound, but will match virtual sensor 2 inbound.

Order in Which Multiple Feature Actions are Applied

The order in which different types of actions in a policy map are performed is independent of the order in which the actions appear in the policy map. Actions are performed in the following order:

•TCP normalization, TCP and UDP connection limits and timeouts, and TCP sequence number randomization

Note When a the security appliance performs a proxy service (such as AAA or CSC) or it modifies the TCP payload (such as FTP inspection), the TCP normalizer acts in dual mode, where it is applied before and after the proxy or payload modifying service.

•CSC

•Application inspection

•IPS

•QoS input policing

•QoS output policing

•QoS priority queue

Default Layer 3/4 Policy Map

The configuration includes a default Layer 3/4 policy map that the security appliance uses in the default global policy. It is called global_policy and performs inspection on the default inspection traffic. You can only apply one global policy, so if you want to alter the global policy, you need to either reconfigure the default policy or disable it and apply a new one.

The default policy map configuration includes the following commands:
policy-map global_policy
 class inspection_default
  inspect dns preset_dns_map 
  inspect ftp 
  inspect h323 h225 
  inspect h323 ras 
  inspect rsh 
  inspect rtsp 
  inspect esmtp 
  inspect sqlnet 
  inspect skinny 
  inspect sunrpc 
  inspect xdmcp 
  inspect sip 
  inspect netbios 
  inspect tftp 
Adding a Layer 3/4 Policy Map

The maximum number of policy maps is 64. To create a Layer 3/4 policy map, perform the following steps:

Step 1 Add the policy map by entering the following command:
hostname(config)# policy-map policy_map_name
The policy_map_name argument is the name of the policy map up to 40 characters in length. All types of policy maps use the same name space, so you cannot reuse a name already used by another type of policy map. The CLI enters policy-map configuration mode.

Step 2 (Optional) Specify a description for the policy map:
hostname(config-pmap)# description text
Step 3 Specify a previously configured Layer 3/4 class map using the following command:
hostname(config-pmap)# class class_map_name
where the class_map_name is the name of the class map you created earlier. See the "Identifying Traffic Using a Layer 3/4 Class Map" section to add a class map.

Step 4 Specify one or more actions for this class map.

•IPS. See the "Diverting Traffic to the AIP SSM" section on page 22-8.

•CSC. See the "Diverting Traffic to the CSC SSM" section on page 22-16.

•TCP normalization. See the "Configuring TCP Normalization" section on page 23-11.

•TCP and UDP connection limits and timeouts, and TCP sequence number randomization. See the "Configuring Connection Limits and Timeouts" section on page 23-14.

•QoS policing and QoS priority. See Chapter 24, "Applying QoS Policies."

•Application inspection. See Chapter 25, "Configuring Application Layer Protocol Inspection."

Note If there is no match default_inspection_traffic command in a class map, then at most one inspect command is allowed to be configured under the class.

Step 5 Repeat Step 3 and Step 4 for each class map you want to include in this policy map.

The following is an example of a policy-map command for connection policy. It limits the number of connections allowed to the web server 10.1.1.1:
hostname(config)# access-list http-server permit tcp any host 10.1.1.1
hostname(config)# class-map http-server
hostname(config-cmap)# match access-list http-server
hostname(config)# policy-map global-policy
hostname(config-pmap)# description This policy map defines a policy concerning connection 
to http server.
hostname(config-pmap)# class http-server
hostname(config-pmap-c)# set connection conn-max 256
The following example shows how multi-match works in a policy map:
hostname(config)# class-map inspection_default
hostname(config-cmap)# match default-inspection-traffic
hostname(config)# class-map http_traffic
hostname(config-cmap)# match port tcp eq 80
hostname(config)# policy-map outside_policy
hostname(config-pmap)# class inspection_default
hostname(config-pmap-c)# inspect http http_map
hostname(config-pmap-c)# inspect sip
hostname(config-pmap)# class http_traffic
hostname(config-pmap-c)# set connection timeout tcp 0:10:0
The following example shows how traffic matches the first available class map, and will not match any subsequent class maps that specify actions in the same feature domain:
hostname(config)# class-map telnet_traffic
hostname(config-cmap)# match port tcp eq 23
hostname(config)# class-map ftp_traffic
hostname(config-cmap)# match po