Catalyst 6500 Series Switch and Cisco 7600 Series Router Firewall Services Module Configuration Guide, 4.1
Using Modular Policy Framework
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Using Modular Policy Framework

Table Of Contents

Using Modular Policy Framework

Information About Modular Policy Framework

Modular Policy Framework Supported Features

Modular Policy Framework Configuration Overview

Default Global Policy

Identifying Traffic (Layer 3/4 Class Map)

Default Class Maps

Maximum Class Maps

Creating a Layer 3/4 Class Map for Through Traffic

Configuring Special Actions for Application Inspections (Inspection Policy Map)

Inspection Policy Map Overview

Defining Actions in an Inspection Policy Map

Identifying Traffic in an Inspection Class Map

Creating a Regular Expression

Creating a Regular Expression Class Map

Defining Actions (Layer 3/4 Policy Map)

Information About Layer 3/4 Policy Maps

Policy Map Guidelines

Feature Directionality

Feature Matching Guidelines within a Policy Map

Order in Which Multiple Feature Actions are Applied

Incompatibility of Certain Feature Actions

Feature Matching Guidelines for Multiple Policy Maps

Default Layer 3/4 Policy Map

Adding a Layer 3/4 Policy Map

Applying Actions to an Interface (Service Policy)

Modular Policy Framework Examples

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 supported features. This chapter includes the following sections:

Information About Modular Policy Framework

Identifying Traffic (Layer 3/4 Class Map)

Configuring Special Actions for Application Inspections (Inspection Policy Map)

Defining Actions (Layer 3/4 Policy Map)

Applying Actions to an Interface (Service Policy)

Modular Policy Framework Examples

Information About Modular Policy Framework

Modular Policy Framework provides a consistent and flexible way to configure FWSM 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. This section includes the following topics:

Modular Policy Framework Supported Features

Modular Policy Framework Configuration Overview

Default Global Policy

Modular Policy Framework Supported Features

Modular Policy Framework supports the following features:

TCP and UDP connection settings, TCP sequence number randomization, and TCP state bypass—See the "Configuring Connection Limits and Timeouts" section on page 21-1, and "Configuring TCP State Bypass" section on page 21-10.

Application inspection—See Chapter 22, "Applying Application Layer Protocol Inspection."

Permitting or Denying Application Types with PISA Integration—See the "Permitting or Denying Application Types with PISA Integration" section on page 21-4.

Modular Policy Framework Configuration Overview

Configuring Modular Policy Framework consists of the following tasks:

1. Identify the traffic on which you want to perform Modular Policy Framework actions by creating Layer 3/4 class maps. For example, you might want to perform actions on all traffic that passes through the FWSM; or you might only want to perform certain actions on traffic from 10.1.1.0/24 to any destination address.

See the "Identifying Traffic (Layer 3/4 Class Map)" section.

2. If one of the actions you want to perform is application inspection, and you want to perform additional actions on some inspection traffic, then create an inspection policy map. The inspection policy map identifies the traffic and specifies what to do with it. For example, you might want to drop all HTTP requests with a body length greater than 1000 bytes.

You can create a self-contained inspection policy map that identifies the traffic directly with match commands, or you can create an inspection class map for reuse or for more complicated matching. See the "Defining Actions in an Inspection Policy Map" section and the "Identifying Traffic in an Inspection Class Map" section.

3. If you want to match text with a regular expression within inspected packets, you can create a regular expression or a group of regular expressions (a regular expression class map). Then, when you define the traffic to match for the inspection policy map, you can call on an existing regular expression. For example, you might want to drop all HTTP requests with a URL including the text "example.com."

See the "Creating a Regular Expression" section and the "Creating a Regular Expression Class Map" section.

4. Define the actions you want to perform on each Layer 3/4 class map by creating a Layer 3/4 policy map. Then, determine on which interfaces you want to apply the policy map using a service policy.

See the "Defining Actions (Layer 3/4 Policy Map)" section and the "Applying Actions to an Interface (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 global_policy
 class inspection_default
  inspect dns maximum-length 512
  inspect ftp
  inspect h323 h225
  inspect h323 ras
  inspect netbios
  inspect rsh
  inspect skinny
  inspect sqlnet
  inspect sunrpc
  inspect tftp
  inspect sip
  inspect xdmcp
service-policy global_policy global

Note See the "Incompatibility of Certain Feature Actions" section for more information about the special match default-inspection-traffic command used in the default class map.


Identifying Traffic (Layer 3/4 Class Map)

A Layer 3/4 class map identifies Layer 3 and 4 traffic to which you want to apply actions. You can create multiple Layer 3/4 class maps for each Layer 3/4 policy map.

This section includes the following topics:

Default Class Maps

Creating a Layer 3/4 Class Map for Through Traffic

Default Class Maps

The configuration includes many internally-created default class maps, including a default Layer 3/4 class map that the FWSM 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


Note See the "Incompatibility of Certain Feature Actions" section for more information about the special match default-inspection-traffic command used in the default class map.


Another class map that exists in the default configuration is called class-default, and it matches all traffic:

class-map class-default
 match any

This class map appears at the end of all Layer 3/4 policy maps and essentially tells the FWSM to not perform any actions on all other traffic. You can use the class-default class map if desired, rather than making your own match any class map.

Default class maps also include inspection class maps.

To view all default class maps, as well as any user-created class maps, enter the show running-config all class-map command.

Maximum Class Maps

The maximum number of class maps of all types is 255 in single mode or per context in multiple mode. Class maps include the following types:

Layer 3/4 class maps

Inspection class maps

Regular expression class maps

match commands used directly underneath an inspection policy map

This limit also includes default class maps of all types. See the "Default Class Maps" section.

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 FWSM 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 13-6 or the "Adding an EtherType Access List" section on page 13-9.

For information about creating access lists with NAT, see the "IP Addresses Used for Access Lists When You Use NAT" section on page 13-3.

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 E-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 FWSM can inspect.

hostname(config-cmap)# match default-inspection-traffic

This command, which is used in the default global policy, is a special CLI shortcut that when used in a policy map, ensures that the correct inspection is applied to each packet, based on the destination port of the traffic. For example, when UDP traffic for port 69 reaches the FWSM, then the FWSM applies the TFTP inspection; when TCP traffic for port 21 arrives, then the FWSM applies the FTP inspection. So in this case only, you can configure multiple inspections for the same class map (with the exception of WAAS inspection, which can be configured with other inspections. See the "Incompatibility of Certain Feature Actions" section for more information about combining actions). Normally, the FWSM does not use the port number to determine the inspection applied, thus giving you the flexibility to apply inspections to non-standard ports, for example.

See the "Default Inspection Policy" section on page 22-4 for a list of default ports. The FWSM 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 and protocols to match, any ports or protocols in the access list are ignored.


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

Configuring Special Actions for Application Inspections (Inspection Policy Map)

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. When the inspection policy map matches traffic within the Layer 3/4 class map for which you have defined an inspection action, then that subset of traffic will be acted upon as specified (for example, dropped or rate-limited).

This section includes the following topics:

Inspection Policy Map Overview

Defining Actions in an Inspection Policy Map

Identifying Traffic in an Inspection Class Map

Creating a Regular Expression

Creating a Regular Expression Class Map

Inspection Policy Map Overview

See the "Inspection Engine Overview" section on page 22-2 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.

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.

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.

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.

Parameters—Parameters affect the behavior of the inspection engine.


Note There are 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.


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 (Optional) Create an inspection class map according to the "Identifying Traffic in an Inspection Class Map" section. Alternatively, you can identify the traffic directly within the policy map.

Step 2 To create the 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 22-6 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 3 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 22, "Applying 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 | drop-connection | mask | reset] [log] | log}

Not all options are available for each application. Other actions specific to the application might also be available. See Chapter 22, "Applying Application Layer Protocol Inspection." for the exact options available.

The drop keyword drops all packets that match.

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.


Note 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 FWSM applies the actions is determined by internal FWSM 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 content length (higher priority) and match content type (lower priority). The sip3 class map includes both commands, but it is ranked according to the lowest priority command, match content type. The sip1 class map includes the highest priority command, so it is matched first, regardless of the order in the policy map. The sip3 class map is ranked as being of the same priority as the sip2 class map, which also contains the match content type command. They are matched according to the order in the policy map: sip3 and then sip2.

class-map inspect type sip match-all sip1
  match content length gt 1000
class-map inspect type sip match-all sip2
  match content type sdp
class-map inspect type sip match-all sip3
  match content length gt 1000
  match content type sdp

policy-map type inspect sip sip
  class sip3
    log
  class sip2
    log
  class sip1
    log


Step 4 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 22, "Applying 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

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 HTTP traffic, you can match a particular URL.


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.

The maximum number of class maps ( Layer 3/4, inspection, and regular expression) is 255 in single mode or per context in multiple mode. This limit includes default class maps. See the "Default Class Maps" section.

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


Step 1 (Optional) If you want to match based on a regular expression, see the "Creating a Regular Expression" section and the "Creating a Regular Expression Class Map" section.

Step 2 Create a class map by entering the following command:

hostname(config)# class-map type inspect application [match-all] 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 22, "Applying 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 CLI enters class-map configuration mode, where you can enter one or more match commands.

Step 3 (Optional) To add a description to the class map, enter the following command:

hostname(config-cmap)# description string

Step 4 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 22, "Applying 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

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 Catalyst 6500 Series Switch and Cisco 7600 Series Router Firewall Services Module Command Reference for performance impact information when matching a regular expression to packets.


Note As an optimization, the FWSM 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 20-1 lists the metacharacters that have special meanings.

Table 20-1 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.

The maximum number of class maps ( Layer 3/4, inspection, and regular expression) is 255 in single mode or per context in multiple mode. This limit includes default class maps. See the "Default Class Maps" section.

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

Defining Actions (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:

Information About Layer 3/4 Policy Maps

Default Layer 3/4 Policy Map

Adding a Layer 3/4 Policy Map

Information About Layer 3/4 Policy Maps

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

Policy Map Guidelines

Feature Directionality

Feature Matching Guidelines within a Policy Map

Order in Which Multiple Feature Actions are Applied

Incompatibility of Certain Feature Actions

Feature Matching Guidelines for Multiple Policy Maps

Policy Map Guidelines

See the following guidelines for using policy maps:

You can only assign one policy map per interface. (However you can create up to 64 policy maps in the configuration.)

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, if supported. See the "Incompatibility of Certain Feature Actions" section.

Feature Directionality

Actions are applied to traffic bidirectionally or unidirectionally depending on whether the service policy is applied to an interface or globally. For a service policy that is applied to an interface, all features are bidirectional; 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. 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.

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 FWSM 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 FWSM also applies the actions for the subsequent class map, if supported. See the "Incompatibility of Certain Feature Actions" section for more information about unsupported combinations.

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.


Note Application inspection includes multiple inspection types, and each inspection type is a separate feature when you consider the matching guidelines above.


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:

1. TCP and UDP connection settings, and TCP state bypass

2. Application inspection (multiple types)

The order of application inspections applied when a class of traffic is classified for multiple inspections is as follows. Only one inspection type can be applied to the same traffic. WAAS inspection is an exception, because it can applied along with other inspections for the same traffic. See the "Incompatibility of Certain Feature Actions" section for more information.

a. CTIQBE

b. DNS

c. FTP

d. GTP

e. H323

f. HTTP

g. ICMP

h. ICMP error

i. ILS

j. MGCP

k. NetBIOS

l. PPTP

m. Sun RPC

n. RSH

o. RTSP

p. SIP

q. Skinny

r. SMTP

s. SNMP

t. SQL*Net

u. TFTP

v. XDMCP

w. DCERPC

3. Permitting or Denying Application Types with PISA Integration

Incompatibility of Certain Feature Actions

Some features are not compatible with each other for the same traffic. For example, you cannot configure PISA integration and inspections for the same set of traffic. Also, most inspections should not be combined with another inspection, so the FWSM only applies one inspection if you configure multiple inspections for the same traffic. In this case, the feature that is applied is the higher priority feature in the list in the "Order in Which Multiple Feature Actions are Applied" section.

For information about compatibility of each feature, see the chapter or section for your feature.


Note The match default-inspection-traffic command, which is used in the default global policy, is a special CLI shortcut to match the default ports for all inspections. When used in a policy map, this class map ensures that the correct inspection is applied to each packet, based on the destination port of the traffic. For example, when UDP traffic for port 69 reaches the FWSM, then the FWSM applies the TFTP inspection; when TCP traffic for port 21 arrives, then the FWSM applies the FTP inspection. So in this case only, you can configure multiple inspections for the same class map. Normally, the FWSM does not use the port number to determine the inspection applied, thus giving you the flexibility to apply inspections to non-standard ports, for example.


An example of a misconfiguration is if you configure multiple inspections in the same policy map and do not use the default-inspection-traffic shortcut. In Example 20-1, traffic destined to port 21 is mistakenly configured for both FTP and HTTP inspection. In Example 20-2, traffic destined to port 80 is mistakenly configured for both FTP and HTTP inspection. In both cases of misconfiguration examples, only the FTP inspection is applied, because FTP comes before HTTP in the order of inspections applied.

Example 20-1 Misconfiguration for FTP packets: HTTP Inspection Also Configured

class-map ftp
   match port tcp 21
class-map http
   match port tcp 21 [it should be 80]
policy-map test
   class ftp
     inspect ftp
   class http
     inspect http

Example 20-2 Misconfiguration for HTTP packets: FTP Inspection Also Configured

class-map ftp
   match port tcp 80 [it should be 21]
class-map http
   match port tcp 80
policy-map test
   class http
     inspect http
   class ftp
     inspect ftp

Feature Matching Guidelines for Multiple Policy Maps

For TCP and UDP traffic (and ICMP when you enable stateful ICMP inspection), service policies operate 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 connection limits on the inside and outside interfaces, but the inside policy sets the maximum connections to 2000 while the outside policy sets the maximum connections to 3000, then a non-stateful Ping might be denied at a lower level if it is outbound than if it is inbound.

Default Layer 3/4 Policy Map

The configuration includes a default Layer 3/4 policy map that the FWSM 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 maximum-length 512
  inspect ftp
  inspect h323 h225
  inspect h323 ras
  inspect netbios
  inspect rsh
  inspect skinny
  inspect sqlnet
  inspect sunrpc
  inspect tftp
  inspect sip
  inspect xdmcp


Note See the "Incompatibility of Certain Feature Actions" section for more information about the special match default-inspection-traffic command used in the default class map.


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 (Layer 3/4 Class Map)" section to add a class map.

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

TCP and UDP connection limits and timeouts, and TCP sequence number randomization. See the "Configuring Connection Limits and Timeouts" section on page 21-1.

TCP state bypass. See the "Configuring TCP State Bypass" section on page 21-10.

Application inspection. See Chapter 22, "Applying Application Layer Protocol Inspection."

Permitting or Denying Application Types with PISA Integration—See the "Permitting or Denying Application Types with PISA Integration" section on page 21-4.


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 port tcp eq 21
hostname(config)# class-map tcp_traffic
hostname(config-cmap)# match port tcp range 1 65535
hostname(config)# class-map udp_traffic
hostname(config-cmap)# match port udp range 0 65535
hostname(config)# policy-map global_policy
hostname(config-pmap)# class telnet_traffic
hostname(config-pmap-c)# set connection timeout tcp 0:0:0
hostname(config-pmap-c)# set connection conn-max 100
hostname(config-pmap)# class ftp_traffic
hostname(config-pmap-c)# set connection timeout tcp 0:5:0
hostname(config-pmap-c)# set connection conn-max 50
hostname(config-pmap)# class tcp_traffic
hostname(config-pmap-c)# set connection timeout tcp 2:0:0
hostname(config-pmap-c)# set connection conn-max 2000

When a Telnet connection is initiated, it matches class telnet_traffic. Similarly, if an FTP connection is initiated, it matches class ftp_traffic. For any TCP connection other than Telnet and FTP, it will match class tcp_traffic. Even though a Telnet or FTP connection can match class tcp_traffic, the FWSM does not make this match because they previously matched other classes.

Applying Actions to an Interface (Service Policy)

To activate the Layer 3/4 policy map, create a service policy that applies it to one or more interfaces or that applies it globally to all interfaces. Interface service policies take precedence over the global service policy for a given feature. For example, if you have a global policy with FTP inspection, and an interface policy with TCP connection settings, then both FTP inspection and TCP connection settings are applied to the interface. However, if you have a global policy with FTP inspection, and an interface policy with FTP inspection, then only the interface policy FTP inspection is applied to that interface.

To create a service policy by associating a policy map with an interface, enter the following command:

hostname(config)# service-policy policy_map_name interface interface_name

To create a service policy that applies to all interfaces that do not have a specific policy, enter the following command:

hostname(config)# service-policy policy_map_name global

By default, the configuration includes a global policy that matches all default application inspection traffic and applies inspection to the traffic globally. 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.

The default service policy includes the following command:

service-policy global_policy global

For example, the following command enables the inbound_policy policy map on the outside interface:

hostname(config)# service-policy inbound_policy interface outside

The following commands disable the default global policy, and enables a new one called new_global_policy on all other FWSM interfaces:

hostname(config)# no service-policy global_policy global
hostname(config)# service-policy new_global_policy global

Modular Policy Framework Examples

This section includes several Modular Policy Framework examples, and includes the following topics:

Applying Inspection to HTTP Traffic Globally

Applying Inspection and Connection Limits to HTTP Traffic to Specific Servers

Applying Inspection to HTTP Traffic with NAT

Applying Inspection to HTTP Traffic Globally

In this example (see Figure 20-1), any HTTP connection (TCP traffic on port 80) that enters the FWSM through any interface is classified for HTTP inspection.

Figure 20-1 Global HTTP Inspection

See the following commands for this example:

hostname(config)# class-map http_traffic
hostname(config-cmap)# match port tcp eq 80

hostname(config)# policy-map http_traffic_policy
hostname(config-pmap)# class http_traffic
hostname(config-pmap-c)# inspect http
hostname(config)# service-policy http_traffic_policy global

Applying Inspection and Connection Limits to HTTP Traffic to Specific Servers

In this example (see Figure 20-2), any HTTP connection destined for Server A (TCP traffic on port 80) that enters the FWSM through the outside interface is classified for HTTP inspection and maximum connection limits.

Any HTTP connection destined for Server B that enters the FWSM through the inside interface is classified for HTTP inspection.

Figure 20-2 HTTP Inspection and Connection Limits to Specific Servers

See the following commands for this example:

hostname(config)# access-list serverA extended permit tcp any host 192.168.1.1 eq 80
hostname(config)# access-list ServerB extended permit tcp any host 10.1.1.2 eq 80

hostname(config)# class-map http_serverA
hostname(config-cmap)# match access-list serverA
hostname(config)# class-map http_serverB
hostname(config-cmap)# match access-list serverB

hostname(config)# policy-map policy_serverA
hostname(config-pmap)# class http_serverA
hostname(config-pmap-c)# inspect http http_map_serverA
hostname(config-pmap-c)# set connection conn-max 100
hostname(config)# policy-map policy_serverB
hostname(config-pmap)# class http_serverB
hostname(config-pmap-c)# inspect http http_map_serverB

hostname(config)# service-policy policy_serverB interface inside
hostname(config)# service-policy policy_serverA interface outside
 
   

Applying Inspection to HTTP Traffic with NAT

In this example, the Host on the inside network has two addresses: one is the real IP address 10.1.1.1, and the other is a mapped IP address used on the outside network, 209.165.200.225 (see Figure 20-3). Because the policy is applied to the inside interface, where the real address is used, then you must use the real IP address in the access list in the class map. If you applied it to the outside interface, you would use the mapped addresses.

Figure 20-3 HTTP Inspection with NAT

See the following commands for this example:

hostname(config)# static (inside,outside) 209.165.200.225 10.1.1.1
hostname(config)# access-list http_client extended permit tcp host 10.1.1.1 any eq 80

hostname(config)# class-map http_client
hostname(config-cmap)# match access-list http_client

hostname(config)# policy-map http_client
hostname(config-pmap)# class http_client
hostname(config-pmap-c)# inspect http

hostname(config)# service-policy http_client interface inside