The documentation set for this product strives to use bias-free language. For the purposes of this documentation set, bias-free is defined as language that does not imply discrimination based on age, disability, gender, racial identity, ethnic identity, sexual orientation, socioeconomic status, and intersectionality. Exceptions may be present in the documentation due to language that is hardcoded in the user interfaces of the product software, language used based on RFP documentation, or language that is used by a referenced third-party product. Learn more about how Cisco is using Inclusive Language.
The Flexible Packet Matching XML Configuration feature allows the use of eXtensible Markup Language (XML) to define traffic classes and actions (policies) to assist in blocking network attacks. The XML file used by Flexible Packet Matching (FPM) is called the traffic classification definition file (TCDF).
The TCDF gives you an alternative to the command-line interface (CLI) as a method to define traffic classification behavior. Traffic classification behavior is identical regardless of the method you use.
Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the "Feature Information for Flexible Packet Matching XML Configuration" section.
Use Cisco Feature Navigator to find information about platform support and Cisco IOS, Catalyst OS, and Cisco IOS software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
•Prerequisites for the Flexible Packet Matching XML Configuration
•Restrictions for the Flexible Packet Matching XML Configuration
•Information About the Flexible Packet Matching XML Configuration
•How to Create and Load Traffic Classification Definition Files for the FPM XML Configuration
•Feature Information for Flexible Packet Matching XML Configuration
•A protocol header definition file (PHDF) relevant to the TCDF must be loaded on the router.
•Although access to an XML editor is not required, using one might make the creation of the TCDF easier.
•You must be familiar with XML file syntax.
TCDF Image Restriction
TCDF is part of the FPM subsystem. FPM is not included in the Cisco 871 securityk9 image; therefore, TCDF parsing is not present in the Cisco 871 securityk9 image.
The Flexible Packet Matching XML Configuration has the following restrictions:
•The FPM TCDF cannot be used to mitigate an attack that requires stateful classification.
•Because FPM is stateless, it cannot keep track of port numbers being used by protocols that dynamically negotiate ports. Thus, when using the FPM TCDF, port numbers must be explicitly specified.
•FPM cannot perform IP fragmentation or TCP flow reassembly.
•Traffic Classification Definition Files for the Flexible Packet Matching XML Configuration
•Protocol Header Definition Files for Traffic Classification Definitions
•Traffic Classification Description File Format and Use
•Traffic Class Definitions for a Traffic Classification Definition File
•Policy Definitions for a Traffic Classification Definition File
FPM uses a TCDF to define policies that can block attacks on the network. FPM is a packet classification feature that allows users to define one or more classes of network traffic by pairing a rich set of standard matching operators with user-defined protocol header fields. FPM users can create their own stateless packet classification criteria and define policies with multiple actions (such as drop, log, or send Internet Control Message Protocol [ICMP] unreachable) to immediately block new viruses, worms, and attacks on the network.
Before the release of the Flexible Packet Matching XML Configuration feature, FPM defined traffic classes (class maps), policies (policy maps), and service policies (attach policy maps to a class maps) through the use of CLI commands. With TCDFs, FPM can use XML as an alternative to the CLI to define classes of traffic and specify actions to apply to the traffic classes. Traffic classification behavior is the same whether you create the behavior using a TCDF or configure it using CLI commands. Once a TCDF is created, it can be loaded on any FPM-enabled device in the network.
TCDFs require that a relevant PHDF is already loaded on the device. A PHDF defines each field contained in the header of a particular protocol. Each field is described with a name, optional comment, an offset (the location of the protocol header field in relation to the start of the protocol header), and the length of the field. The total length is specified at the end of each PHDF.
The description of a traffic class in a TCDF file can contain header fields defined in a PHDF. If the PHDF is loaded on the router, the class specification to match begins with a list of the protocol headers in the packet. In the TCDF, the traffic class is associated with a policy that binds the match to an action, such as drop, log, or send ICMP unreachable.
FPM provides ready-made definitions for these standard protocols, which can be loaded onto the router with the load protocol command: ether.phdf, ip.phdf, tcp.phdf, and udp.phdf. You can also write your own custom PHDFs using XML if one is required for the TCDF.
Note Because PHDFs are defined via XML, they are not shown in a running configuration.
In the TCDF, you can define one or more classes of traffic and policies that describe specified actions for each class of traffic. The TCDF is an XML file that you create in a text file or with an XML editor. The file that you create must have a filename that has the .tcdf extension.
The TCDF has the following basic format. XML tags are shown in bold text for example purposes only.
<tdcf>
<class ...> ... </class>
...
<policy> ... </policy>
...
</tdcf>
For a traffic class, you can identify a match for any field or fields against any part of the packet.
Note FPM is stateless and cannot be used to mitigate an attack that requires stateful classification, that is classify across IP fragments, across packets in a TCP stream, or peer-to-peer protocol elements.
Policies can be anything from access control, quality of service (QoS), or even routing decisions. For FPM, the associated actions (policies) might include permit, drop, log, or send ICMP unreachable.
Once loaded, the TCDF-defined classes and policies can be applied to any interface or subinterface and behave in an identical manner as the CLI-defined classes and policies. You can define policies in the TCDF and apply then to any entry point to the network to block new attacks.
A class can be any traffic stream of interest. You define a traffic stream of interest by matching a particular interface or port, a source address or destination IP address, a protocol or an application. The following sections contain information you should understand before you define the traffic class in the TCDF for FPM configuration:
•Class Element Attributes for a Traffic Classification Definition File
•Match Element for a Traffic Classification Definition File
•Operator Element Attributes for a Traffic Classification Definition File
Table 1 lists and describes the attributes that you can associate with the class element in a TCDF for the FPM XML configuration. The class element contains attributes you can use to specify the traffic class name, its description and type, where to look in the packet, what kind of match, and when the actions should apply to the traffic.
For example, XML syntax for a stack class describing an IP, User Datagram Protocol (UDP), Simple Management Protocol (SNMP) stack might look like this:
<class name="snmp-stack" type="stack">
<match>
<eq field="ip.protocol" value="x"></eq>
<eq field="udp.dport" value="161"></eq>
</match>
</class>
The match element in the TCDF for FPM XML configuration contains operator elements. Operator elements are the following: eq (equal to), neq (not equal to), lt (less than), gt (greater than), range (a value in a specific range, for example, range 1 - 25), and regex (regular expression string with a maximum length of 32 characters).
In following sections, these various operators are collectively called the operator element.
Table 2 lists and describes direct matching attributes that you can associate with the operator element in a TCDF for the FPM XML configuration.
A policy is any action that you apply to a class. You should understand the following information before defining the policy in a TCDF for the FPM XML configuration:
•Policy Element Attributes for a Traffic Classification Definition File
•Action Element for a Traffic Classification Definition File
•Traffic Classification Definition File Syntax Guidelines
Policies can be anything from access control, QoS, or even routing decisions. For FPM, the associated actions or policies might include drop, log, or send ICMP unreachable. Policies describe the action to take to mitigate attacks on the network.
Table 3 lists and describes the attributes that you can use with the policy element in the TDCF for FPM XML configuration.
The policy name in this example is sql-slammer, and the action defined for the policy is to drop the packet. This action is to be applied to the class that has the same name as the policy (class name= "sql-slammer").
<policy name="sql-slammer">
<class name="sql-slammer"></class>
<action>drop</action>
</policy>
The action element is used to specify actions to associate with a policy. The policy with the action element is applied to a defined class. The action element can contain any of the following: permit, drop, Log, SendBackIcmp, set, RateLimit, alarm, ResetTcpConnection, and DropFlow. For example:
<action>
log
</action>
The following list describes required and optional syntax for the TCDF:
•The TCDF filename must end in the .tcdf extension, for example, sql_slammer.tcdf.
•The TCDF contains descriptions for one or more traffic classes and one or more policy actions.
•The file is encoded in the XML notation.
•The TCDF file should begin with the following version encoding:
<?xml version="1.0" encoding="UTF-8"?>
The TCDF is used to define traffic classes and the associated policies with specified actions for the purpose of blocking new viruses, worms, and attacks on the network.
The TCDF is configured in a text or XML editor. The syntax of the TCDF must comply with the XML Version 1.0 syntax and the TCDF schema. For information about Version 1.0 XML syntax, see the document at the following url:
1. Open a text file or an XML editor and begin the file with the XML version and encoding declaration.
2. Identify the file as a TCDF.
3. Define the traffic class of interest.
4. Identify matching criteria for the defined class of traffic.
5. Define the action to apply to the defined class.
6. End the traffic classification definition.
7. Save the TCDF file with a filename that has a .tcdf extension.
Step 1 Open a text file or an XML editor and begin the file with the XML version and encoding declaration.
<?xml version="1.0" encoding="UTF-8"?>
Step 2 Identify the file as a TCDF. For example:
<tcdf>
Step 3 Define the traffic class of interest.
For example, a stack class describing an IP and UDP stack might be described as follows. In this example, the name of the traffic class is "ip-udp," and the class type is "stack."
<class name="ip-udp" type="stack"></class>
In the following example, the name of the traffic class is slammer, the class type is access control, and the match criteria is all:
<class name="slammer" type="access-control" match="all"></class>
Step 4 Identify matching criteria for the defined classes of traffic. For example:
<class name="ip-udp" type="stack">
<match>
<eq field="ip.protocol" value="0x11" next="udp"></eq>
</match>
</class>
<class name="slammer" type="access-control" match="all">
<match>
<eq field="udp.dest-port" value="0x59A"></eq>
<eq field="ip.length" value="0x194"></eq>
<eq start="l3-start" offset="224" size="4" value="0x00401010"></eq>
</match>
</class>
The traffic of interest in this TCDF matches fields defined in the PHDF files, ip.phdf and udp.phdf. The matching criteria for slammer packets is a UDP destination port number 1434 (0x59A), an IP length not to exceed 404 (0x194) bytes, and a Layer 3 position with a pattern 0x00401010 at 224 bytes from start (offset) of the IP header.
Step 5 Define the action to apply to the defined class. For example:
<policy name="fpm-udp-policy">
<class name="slammer"></class>
<action>Drop</action>
</policy>
The policy name in this example is fpm-udp-policy, and the action defined for the policy is to drop the packet. This action is to be applied to the class that has the name slammer.
Step 6 End the traffic classification definition. For example:
</tcdf>
Step 7 Save the TCDF file with a filename that has a .tcdf extension, for example: slammer.tcdf.
1. enable
2. show protocol phdf protocol-name
3. configure terminal
4. load protocol location:filename
5. load classification location:filename
6. end
7. show class-map [type {stack | access-control}] [class-map-name]
The following is sample output from a show class-map command that displays the traffic classes defined in the TCDF after it is loaded on the router:
Router# show class-map
.
.
.
class-map type stack match-all ip-udp
match field IP protocol eq 0x11 next UDP
class-map type access-control match-all slammer
match field UDP dest-port eq 0x59A
match field IP length eq 0x194
match start l3-start offset 224 size 4 eq 0x4011010
.
.
.
After you have defined the TCDF, you must apply that policy to an interface as shown in the following task "Associating a Traffic Classification Definition File with an Interface or Subinterface."
The TCDP and FPM must be configured on the device.
1. enable
2. configure terminal
3. interface type slot/port
4. service-policy [type access-control] {input | output} policy-map-name
5. end
6. show policy-map interface [type access-control] interface-name slot/port [input | output]
1. enable
2. show class-map [type {stack | access-control}] [class-map-name]
3. show class-map type stack [class-map-name]
4. show class-map type access-control [class-map-name]
5. show policy-map [policy-map]
6. exit
Step 1 enable
Use this command to enable privileged EXEC mode. Enter your password if prompted. For example:
Router> enable
Router#
Step 2 show class-map [type {stack | access-control}] [class-map-name]
Use this command to verify that a class defined in the TCDF file is available on the device. For example:
Router# show class-map
.
.
.
class-map type stack match-all ip-udp
match field IP protocol eq 0x11 next UDP
class-map type access-control match-all slammer
match field UDP dest-port eq 0x59A
match field IP length eq 0x194
match start l3-start offset 224 size 4 eq 0x4011010
.
.
.
Step 3 show class-map type stack [class-map name]
Use this command to display the stack type defined for the class of traffic in the TCDF file. For example:
Router# show class-map type stack ip-udp
class-map type stack match-all ip-udp
match field IP protocol eq 0x11 next UDP
Step 4 show class-map type access-control [class-map-name]
Use this command to display the access type defined for the class in the TCDF file. For example:
Router# show class-map type access-control slammer
class-map type access-control match-all slammer
match field UDP dest-port eq 0x59A
match field IP length eq 0x194
match start l3-start offset 224 size 4 eq 0x4011010
Step 5 show policy-map [policy-map]
Use this command to display the contents of a policy map defined in the TCDF. For example:
Router# show policy-map fpm-udp-policy
policy-map type access-control fpm-udp-policy
class slammer
drop
Step 6 exit
Use this command to exit to user EXEC mode. For example:
Router# exit
Router>
Note The TCDF files are created in a text file or with an XML editor. In the following examples, XML tags are shown in bold text and field names in italic text. The values for the attributes are entered in quotation marks ("value").
The following example shows how to create and load a TCDF for slammer packets (UDP 1434) for the FPM configuration. The match criteria defined within the class element is for slammer packets with an IP length not to exceed 404 (0x194) bytes, UDP destination port 1434 (0x59A), and pattern 0x00401010 at 224 bytes from start of IP header. This example also shows how to define the policy "sql-slammer" with the action to drop slammer packets.
<?xml version="1.0" encoding="UTF-8"?>
<tcdf>
<class name="ip-udp" type="stack">
<match>
<eq field="ip.protocol" value="0x11" next="udp"></eq>
</match>
</class>
<class name="slammer" type="access-control" match="all">
<match>
<eq field="udp.dest-port" value="0x59A"></eq>
<eq field="ip.length" value="0x194"></eq>
<eq start="l3-start" offset="224" size="4" value="0x00401010"></eq>
</match>
</class>
<policy type="access-control" name="fpm-udp-policy">
<class name="slammer"></class>
<action>Drop</action>
</policy>
</tcdf>
The following example shows how to load the TCDF file onto the device and apply the policy defined in the file to the interface Gigabit Ethernet 0/1:
configure terminal
load classification localdisk1:sql-slammer.tcdf
policy-map type access-control my-policy-1
class ip-udp
service-policy fpm-udp-policy
interface gigabitEthernet 0/1
service-policy type access-control input my-policy-1
end
The following example shows how to create and load a TCDF for MyDoom packets in a text file or XML editor for the FPM XML configuration. The match criteria for the MyDoom packets are as follows:
•90 > IP length > 44
•pattern 0x47455420 at 40 bytes from start of IP header
or
•IP length > 44
•pattern 0x47455420 at 40 bytes from start of IP header
<tcdf>
<class name="md-stack" type="stack">
<match>
<eq field="ip.protocol" value="6" next="tcp"></eq>
</match>
</class>
<class type="access-control" name="mydoom1">
<match>
<gt field="ip.length" value="44"/>
<lt field="ip.length" value="90"/>
<eq start="ip.version" offset="tcp.headerlength*4+20" size="4"
value="0x47455420"/>
</match>
</class>
<class type="access-control" name="mydoom2">
<match>
<gt field="ip.length" value="44"/>
<eq start="ip.version" offset="tcp.headerlength*4+58" size="4"
value="0x6d3a3830"/>
<eq start="ip.version" offset="tcp.headerlength*4+20" size="4"
value="0x47455420"/>
</match>
</class>
<policy name="fpm-md-stack-policy">
<class name="mydoom1"></class>
<action>drop</action>
</policy>
<policy name="fpm-md-stack-policy">
<class name="mydoom2"></class>
<action>drop</action>
</policy>
</tcdf>
The following example shows how to load the TCDF file onto the device and apply the policy defined in the file to the interface Ethernet 0/1:
configure terminal
load classification localdisk1:sql-slammer.tcdf
policy-map type access-control my-policy-2
class md-stack
service-policy fpm-md-stack-policy
interface Ethernet 0/1
service-policy type access-control input my-policy-2
end
|
|
---|---|
Cisco IOS commands |
|
Additional configuration information for class maps and policy maps |
|
Information about and configuration tasks for FPM |
"Flexible Packet Matching" module |
|
|
---|---|
No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature. |
— |
|
|
---|---|
No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature. |
— |
Table 4 lists the release history for this feature.
Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
Note Table 4 ists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.
|
|
|
---|---|---|
Flexible Packet Matching XML Configuration |
12.4(6)T |
The Flexible Packet Matching XML Configuration feature provides an Extensible Markup Language (XML)-based configuration file for Flexible Packet Matching (FPM) that can be used to define traffic classes and actions (policies) to assist in the blocking of attacks on a network. The XML file used by FPM is called the traffic classification definition file (TCDF). The TCDF gives you an alternative to the command-line interface (CLI) as a method to define traffic classification behavior. Traffic classification behavior is identical regardless of the method you use. This feature was introduced in Cisco IOS Release 12.4(6)T. The following sections provide information about this feature: •Information About the Flexible Packet Matching XML Configuration •How to Create and Load Traffic Classification Definition Files for the FPM XML Configuration The following command was introduced by this feature: load classification. |