Control Plane Policing
http://www.cisco.com/en/US/docs/ios/12_3t/12_3t4/feature/guide/gtrtlimt.html
Table Of Contents
Control Plane Policing
Contents
Prerequisites for Control Plane Policing
Restrictions for Control Plane Policing
Information About Control Plane Policing
Benefits of Control Plane Policing
Terms to Understand
Control Plane Security and Packet QoS Overview
Aggregate Control Plane Services
Distributed Control Plane Services
Using Distributed CP Services
Output Rate-Limiting and Silent Mode Operation
How to Use the Control Plane Policing Feature
Defining Aggregate Control Plane Services
Prerequisites
Restrictions
Defining Distributed Control Plane Services
Prerequisites
Restrictions
Verifying Aggregate CP Services
Examples
Verifying Distributed CP Services
Examples
Configuration Examples for Control Plane Policing
Configuring Control Plane Policing on Input Telnet Traffic: Example
Configuring Control Plane Policing on Output ICMP Traffic: Example
Additional References
Related Documents
Standards
MIBs
RFCs
Technical Assistance
Command Reference
control-plane
service-policy (control-plane)
show policy-map control-plane
Control Plane Policing
Part Number OL-8695-01 (Rev A0), January 19, 2006
The Control Plane Policing feature allows users to configure a quality of service (QoS) filter that manages the traffic flow of control plane packets to protect the control plane of Cisco IOS routers and switches against reconnaissance and denial-of-service (DoS) attacks. In this way, the control plane (CP) can help maintain packet forwarding and protocol states despite an attack or heavy traffic load on the router or switch.
History for the Control Plane Policing Feature
|
Release
|
Modification
|
| 12.2(18)S |
This feature was introduced. |
| 12.3(4)T |
Control Plane Policing was integrated into Cisco IOS Release 12.3(4)T, and the output rate-limiting (silent mode operation) feature was added. |
| 12.3(7)T |
CISCO-CLASS-BASED-QOS-MIB was extended to manage control plane QoS policies, and the police rate command was introduced to support traffic policing on the basis of packets per second for control plane traffic. |
| 12.0(29)S |
The Control Plane Policing feature was integrated into Cisco IOS Release 12.0(29)S. |
| 12.2(18)SXD1 |
The Control Plane Policing feature was integrated into Cisco IOS Release 12.2(18)SXD1. |
| 12.0(30)S |
Support for distributed control plane services on the Cisco 12000 series Internet router was added. |
| 12.2(27)SBC |
This feature was integrated into Cisco IOS Release 12.2(27)SBC. |
| 12.0(32)S |
Support for aggregate control plane services on the Cisco 10720 Internet router was added. |
Finding Support Information for Platforms and Cisco IOS Software Images
Use Cisco Feature Navigator to find information about platform support and Cisco IOS software image support. Access Cisco Feature Navigator at http://www.cisco.com/go/fn. You must have an account on Cisco.com. If you do not have an account or have forgotten your username or password, click Cancel at the login dialog box and follow the instructions that appear.
Contents
•
Prerequisites for Control Plane Policing
•Restrictions for Control Plane Policing
•Information About Control Plane Policing
•How to Use the Control Plane Policing Feature
•Configuration Examples for Control Plane Policing
•Additional References
•Command Reference
Prerequisites for Control Plane Policing
•Understanding the concepts and general configuration procedure (class map and policy map) for applying quality-of-service (QoS) policies on a router
For information about Cisco IOS QoS and the procedure for configuring QoS in your network using the modular QoS command-line interface (MQC), refer to Cisco IOS Quality of Service Solutions Configuration Guide, Release 12.3.
Restrictions for Control Plane Policing
Aggregate and Distributed Control Plane Policing
Aggregate policing is supported in Cisco IOS Release 12.0(29)S, Cisco IOS Release 12.2(18)S, and Cisco IOS Release 12.3(4)T and later releases.
Distributed policing is supported only in Cisco IOS Release 12.0(30)S and later Cisco IOS 12.0S releases.
Output Rate-Limiting Support
Output rate-limiting is performed in silent (packet discard) mode. Silent mode enables a router to silently discard packets using policy maps applied to output control plane traffic with the service-policy output command. For more information, see Output Rate-Limiting and Silent Mode Operation.
Output rate-limiting (policing) in silent mode is supported only in:
•Cisco IOS Release 12.2(25)S and later Cisco IOS 12.2S releases
•Cisco IOS Release 12.3(4)T and later Cisco IOS 12.3T releases
Output rate-limiting is not supported for distributed control plane services in Cisco IOS 12.0S releases or in Cisco IOS 12.2SX releases.
Output rate-limiting is not supported on the Cisco 7500 series and Cisco 10720 Internet router.
Modular QoS Restrictions
The Control Plane Policing feature requires the modular QoS command-line interface (CLI) (MQC) to configure packet classification and policing. All restrictions that apply when you use the MQC to configure policing also apply when you configure control plane policing. Only two MQC actions are supported in policy maps—police and drop.
Note On the Cisco 10720 Internet router, only the police command, not the drop command, is supported in policy maps. In addition, in a QoS service policy attached to the 10720 control plane, the police command does not support set actions as arguments in conform-action, exceed-action, and violate-action parameters.
Features that require network-based application recognition (NBAR) classification may not work well at the control plane level. The following classification (match) criteria are supported on all platforms:
•Standard and extended IP access lists (ACLs)
•In class-map configuration mode: match ip dscp, match ip precedence, and match protocol arp commands.
Note In the Cisco IOS 12.2SX release, the match protocol arp command is not supported.
On the Cisco 10720 Internet router, the following MQC commands are also supported in class-map configuration mode: match input-interface, match mpls experimental, match protocol ipv6, and match qos-group. When using these commands for control plane policing on the Cisco 10720 Internet router, note the following restrictions:
•Packet classification using match criteria is not supported for packets that cannot be classified in the 10720 data path, such as unknown Layer 2 encapsulation and IP options.
•The following IPv6 fields are not be supported in packet classification for IPv6 QoS on the Cisco 10720 Internet router and are, therefore, not supported for control plane policing:
–IPv6 source and destination addresses
–Layer 2 class of service (CoS)
–IPv6 routing header flag
–IPv6 undetermined transport flag
–IPv6 flow label
–IP Real-Time transport Protocol (RTP)
Note Packets that are not supported for QoS packet classification on the Cisco 10720 Internet router are not policed in the default traffic class for control plane policing.
CISCO-CLASS-BASED-QOS-MIB Control Plane Support
In Cisco IOS Release 12.3(7)T and later Cisco IOS 12.3T releases, the CISCO-CLASS-BASED-QOS-MIB is extended to manage control plane QoS policies and provide information about the control plane.
Cisco IOS Release 12.2(18)SXD1
In Cisco IOS Release 12.2(18)SXD1 and later releases, Hardware Control Plane Interface for Control Plane Policing has the following restrictions:
•Supported only with Supervisor Engine 720. Not supported with Supervisor Engine 2.
•Does not support CoPP output rate limiting (policing).
•Does not support the CoPP silent operation mode.
•Cisco IOS Release 12.2(18)SXD1 and later releases automatically install the CoPP service policy on all DFC-equipped switching modules.
For more information about Control Plane Policing in Cisco IOS Release 12.2(18)SXD1 and later releases, see either of these publications:
•For Control Plane Policing on Catalyst 6500 series switches:
http://www.cisco.com/univercd/cc/td/doc/product/lan/cat6000/122sx/swcg/dos.htm
•For Control Plane Policing on Cisco 7600 series routers:
http://www.cisco.com/univercd/cc/td/doc/product/core/cis7600/software/122sx/swcg/dos.htm
Information About Control Plane Policing
To configure the Control Plane Policing feature, you should understand the following concepts:
•Benefits of Control Plane Policing
•Terms to Understand
•Control Plane Security and Packet QoS Overview
•Aggregate Control Plane Services
•Distributed Control Plane Services
•Using Distributed CP Services
•Output Rate-Limiting and Silent Mode Operation
Benefits of Control Plane Policing
Configuring the Control Plane Policing feature on your Cisco router or switch provides the following benefits:
•Protection against DoS attacks at infrastructure routers and switches
•QoS control for packets that are destined to the control plane of Cisco routers or switches
•Ease of configuration for control plane policies
•Better platform reliability and availability
Terms to Understand
Because different platforms can have different architectures, the following set of terms is defined. Figure 1 illustrates how control plane policing works.
Figure 1 Layout of Control Plane, Central Switch Engine, Distributed Switch Engines, and Line Cards on a Router
•Control plane (CP)—A collection of processes that run at the process level on the route processor (RP). These processes collectively provide high-level control for most Cisco IOS functions.
•Central switch engine—A device that is responsible for high-speed routing of IP packets. It also typically performs high-speed input and output services for nondistributed interfaces. (See nondistributed line cards.) The central switch engine is used to implement aggregate CP protection for all interfaces on the router.
Note All IP packets that are destined for the CP should pass through the central switch engine before they are forwarded to the process level.
On the Cisco 10720 Internet router, control plane policing is implemented on Cisco Parallel eXpress Forwarding (PXF) in a Toaster-based architecture. PXF is a hardware-based central switch engine that can filter traffic at a higher rate than the route processor. PXF switches all data traffic separately from the route processor. PXF packet processing occurs at an intermediate step between the nondistributed line cards and route processor shown in Figure 1. In addition to the regular punting, PXF also punts certain types of packets (such as unknown Layer 2 encapsulation and packets with IP options) to the RP for further processing at interrupt level. For more information, refer to Queueing Architecture and Modular Quality of Service (QoS) on the Cisco 10720 Internet Router.
Note On the Cisco 10720 Internet router, you can configure enhanced RP protection by using the ip option drop command to drop IPv4 packets with IP options that are punted to the RP by PXF. Tunneled IPv4 packets and IPv4 packets with an unsupported encapsulation method are not dropped. For more information, refer to ACL IP Options Selective Drop.
•Distributed switch engine—A device that is responsible for high-speed switching of IP packets on distributed line cards without using resources from the central switch engine. It also typically performs input and output services for the line card. Each distributed switch engine is used to implement distributed CP services for all ports on a line card. Input CP services distribute the processing load across multiple line cards and conserve vital central switch engine resources. Distributed CP services are optional; however, they provide a more refined level of service than aggregate services.
•Nondistributed line cards—Line cards that are responsible for receiving packets and occasionally performing input and output services. All packets must be forwarded to the central switch engine for a routing or switching decision. Aggregate CP services provide coverage for nondistributed line cards.
Note Distributed CP services are supported only in 12.0(30)S and later 12.0S releases.
Control Plane Security and Packet QoS Overview
To protect the CP on a router from DoS attacks and to provide packet QoS, the Control Plane Policing feature treats the CP as a separate entity with its own ingress (input) and egress (output) ports, which are like ports on a router and switch. Because the Control Plane Policing feature treats the CP as a separate entity, a set of rules can be established and associated with the ingress and egress port of the CP.
These rules are applied only after the packet has been determined to have the CP as its destination or when a packet exits from the CP. Thereafter, you can configure a service policy to prevent unwanted packets from progressing after a specified rate limit has been reached; for example, a system administrator can limit all TCP/SYN packets that are destined for the CP to a maximum rate of 1 megabit per second.
Input CP services are executed after router input port services and a routing decision on the input path have been made. As shown in Figure 2, CP security and packet QoS are applied on:
•An aggregate level by the central switch engine and applied to all CP packets received from all line cards on the router (see Aggregate Control Plane Services)
•A distributed level by the distributed switch engine of a line card and applied to all CP packets received from all interfaces on the line card (see Distributed Control Plane Services)
Figure 2 Input Control Plane Services: Aggregate and Distributed Services
The following types of Layer 3 packets are forwarded to the control plane and processed by aggregate and distributed control plane policing:
•Routing protocol control packets
•Packets destined for the local IP address of the router
•Packets from management protocols (such as Simple Network Management Protocol [SNMP], Telnet, and secure shell [SSH])
Note Ensure that Layer 3 control packets have priority over other packet types that are destined for the control plane.
Aggregate Control Plane Services
Aggregate control plane services provide control plane policing for all CP packets received from all line-card interfaces on the router.
The central switch engine executes normal input port services and makes routing decisions for an incoming packet: if the packet is destined for the CP, aggregate services are performed. Because CP traffic from all line cards must pass through aggregate CP services, these services manage the cumulative amount of CP traffic that reaches the CP.
Aggregate CP service steps are as follows:
1. The line card receives a packet and delivers it to the central switch engine.
Note Before the packet is sent to the central switch engine, additional processing may be necessary for platforms that support hardware-level policing or platform-specific aggregate policing. It is possible that the packet may undergo multiple checks before it undergoes the generic Cisco IOS check.
2. The interfaces perform normal (interface-level) input port services and QoS.
3. The central switch engine performs Layer 3 switching or makes a routing decision, determining whether or not the packet is destined for the CP.
4. The central switch engine performs aggregate CP services for all CP packets.
5. On the basis of the results of the aggregate CP services, the central switch engine either drops the packet or delivers the packet to the CP for final processing.
Functionality Highlights of Aggregate CP Services
The following list highlights the functionality of aggregate CP services:
•Defined for a single input interface, such as the CP, and represents an aggregate for all ports on a router.
•Modular QoS is used to define CP services. Class maps and policy maps for both DoS protection and packet QoS are defined for a single aggregate CP service policy.
•Modular QoS does not prevent a single bad port from consuming all allocated bandwidth. Class maps that match an interface or subinterface may be able to constrain the contribution of each interface through an interface-specific policy map.
Distributed Control Plane Services
Distributed control plane services provide control plane policing for all CP packets received from the interfaces on a line card.
A distributed switch engine executes normal input port services and makes routing decisions for a packet: if the packet is destined for the CP, distributed CP services are performed. Afterwards, CP traffic from each line card is forwarded to the central switch engine where aggregate CP services are applied.
Note Distributed CP services may also forward conditioned packets to the central switch engine. In this case, aggregate CP services are also performed on the conditioned CP traffic.
Distributed CP service steps are as follows:
1. A line card receives a packet and delivers it to the distributed switch engine.
2. The distributed switch engine performs normal (interface-level) input port services and QoS.
3. The distributed switch engine performs Layer 2 or Layer 3 switching, or makes a routing decision, determining whether or not the packet is destined for the CP.
4. The distributed switch engine performs distributed CP services for all CP packets.
5. On the basis of the results of the distributed CP services, the distributed switch engine either drops the packet or marks the packet and delivers it to the central switch engine for further processing.
6. The central switch engine performs aggregate CP services and delivers the packet to the CP for final processing.
Functionality Highlights of Distributed CP Services
The following list highlights the functionality of distributed CP services:
•Distributed CP services are defined for a single input interface, such as the distributed CP, and represent an aggregate for all ports on a line card.
•Modular QoS is used to define CP services. Class maps and policy maps for both DoS protection and packet QoS are defined for a single distributed CP service policy. Each line card may have a unique CP service policy that applies traffic classifications, QoS policies and DoS services to packets received from all ports on the line card in an aggregate way.
•Modular QoS does not prevent one bad port from consuming all allocated bandwidth on a line card. Class maps that match an interface or subinterface may be able to constrain the contribution of each interface through an interface-specific policy map.
Distributed CP services allow you to limit the number of CP packets forwarded from a line card to the central switch engine. The total amount of CP packets received from all line cards on a router may exceed aggregate CP levels.
Using Distributed CP Services
The purpose of CP protection and packet QoS is to apply sufficient control to the packets that reach the control plane. To successfully configure this level of CP protection, you must:
•Apply traditional QoS services using the modular QoS command-line interface to CP packets.
•Protect the path to the control plane against indiscriminate packet dropping due to resource exhaustion. If packets are not dropped according to user-defined QoS policies, but are dropped due to a resource limitation, the QoS policy is not maintained.
Distributed CP services allow you to configure specific CP services that are enforced at the line card level and required for the following reasons:
•While under a DoS attack, line card resources may be consumed. In this case, you must configure a drop policy to identify important packets. The drop policy ensures that all important packets arrive to the central switch engine for aggregate CP protection and later to the CP. Distributed CP services allow routers to apply the appropriate drop policy when resources are consumed, and therefore maintain the desired QoS priorities. If a line card indiscriminately drops packets, the aggregate CP filter becomes ineffective and the QoS priorities are no longer maintained.
•It is not possible to prevent one interface from consuming all aggregate CP resources. A DoS attack on one port may negatively impact CP processing of traffic from other ports. Distributed CP services allow you to limit the amount of important traffic forwarded by a line card to the CP. For example, you can configure a layered approach in which the combined rates of all line cards is over-subscribed compared to the aggregate rate. The rate of each individual line card would be below the aggregate rate, but combined together, the rates of all line cards exceed it. This over-subscription model is commonly used for other resource-related functions and helps limit the contribution of CP packets from any one line card.
•Distributed CP services provide for slot-level (line card) filtering. Customer-facing interfaces may have greater security requirements (with more restrictions or for billing reasons) than network-facing interfaces to backbone devices.
•Because distributed CP protection allows you to configure packet filters on a per-line card basis, processing cycles on line cards may offload aggregate level processing. You can configure Border Gateway Protocol (BGP) filtering at the distributed level for interfaces that use BGP, allowing the aggregate level to filter packets with the remaining filter requirements. Or you can configure identical filters for distributed and aggregate CP services with a distributed packet marking scheme that informs the aggregate filter that a packet has already been checked. Distributed CP service processing further reduces aggregate processing and can significantly reduce the load on aggregate CP services.
Output Rate-Limiting and Silent Mode Operation
A router is automatically enabled to silently discard packets when you configure output policing on control plane traffic, using the service-policy output policy-map-name command.
Rate-limiting (policing) of output traffic from the CP is performed in silent mode. In silent mode, a router that is running Cisco IOS software operates without sending any system messages. If a packet that is exiting from the control plane is discarded for output policing, you do not receive an error message.
When control plane policing is configured for output traffic, error messages are not generated in the following cases:
•Traffic that is being transmitted to a port to which the router is not listening
•A connection to a legitimate address and port that is rejected because of a malformed request
Note The silent mode functionality and output policing on CP traffic are supported only in:
- Cisco IOS Release 12.2(25)S and later Cisco IOS 12.2S releases.
- Cisco IOS Release 12.3(4)T and later Cisco IOS 12.3T releases.
Silent mode and output policing on CP traffic are not supported for distributed control plane services.
How to Use the Control Plane Policing Feature
This section documents the following procedures:
•Defining Aggregate Control Plane Services
•Defining Distributed Control Plane Services
•Verifying Aggregate CP Services
•Verifying Distributed CP Services
Defining Aggregate Control Plane Services
Perform this task to configure aggregate CP services, such as packet rate control and silent packet discard, for the active route processor.
Prerequisites
Before you enter control-plane configuration mode to attach an existing QoS policy to the control plane, you must first create the policy using MQC to define a class map and policy map for control plane traffic.
For information about how to classify traffic and create a QoS policy, refer to the "Modular Quality of Service Command-Line Interface" chapter in the Cisco IOS Quality of Service Solutions Configuration Guide.
Restrictions
•Platform-specific restrictions, if any, are checked when the service policy is applied to the control plane interface.
•Support for output policing is available only in Cisco IOS Release 12.3(4)T and later T-train releases. (Note that output policing does not provide any performance benefits. It simply controls the information that is leaving the device.)
SUMMARY STEPS
1. enable
2. configure terminal
3. control-plane
4. service-policy {input | output} policy-map-name
DETAILED STEPS
|
Command or Action
|
Purpose
|
|
|---|---|---|
| Step 1 |
enable
Example:
Router> enable |
Enables privileged EXEC mode. • |
| Step 2 |
configure terminal
Example:
Router# configure terminal |
Enters global configuration mode. |
| Step 3 |
control-plane
Example:
Router(config)# control-plane |
Enters control-plane configuration mode to attach a QoS policy that manages CP traffic. |
| Step 4 |
service-policy {input | output}policy-map-name
Example:
Router(config-cp)# service-policy input control-plane-policy |
Attaches a QoS service policy to the control plane. • • • |
Defining Distributed Control Plane Services
Perform this task to configure distributed CP services, such as packet rate control, for packets that are destined for the CP and sent from the interfaces on a line card.
Prerequisites
Before you enter control-plane configuration mode to attach an existing QoS policy for performing distributed control-plane services, you must first create the policy using MQC to define a class map and policy map for control-plane traffic.
For information about how to classify traffic and create a QoS policy, refer to the "Modular Quality of Service Command-Line Interface" chapter in the Cisco IOS Quality of Service Solutions Configuration Guide.
Restrictions
•Platform-specific restrictions, if any, are checked when the service policy is applied to the control plane interface.
•Support for output policing is available only in Cisco IOS Release 12.3(4)T and later T-train releases. (Note that output policing does not provide any performance benefits. It simply controls the information that is leaving the device.)
•With Cisco IOS 12.2SX releases, Supervisor Engine 720 automatically installs the service policy on all DFC-equipped switching modules.
SUMMARY STEPS
1. enable
2. configure terminal
3. control-plane [slot slot-number]
4. service-policy input policy-map-name
DETAILED STEPS
|
Command or Action
|
Purpose
|
|
|---|---|---|
| Step 1 |
enable
Example:
Router> enable |
Enables privileged EXEC mode. • |
| Step 2 |
configure terminal
Example:
Router# configure terminal |
Enters global configuration mode. |
| Step 3 |
control-plane [slot slot-number]
Example:
Router(config)# control-plane slot 3 |
Enters control-plane configuration mode to attach a QoS policy to manage CP traffic on the line card in the specified slot. |
| Step 4 |
service-policy input policy-map-name
Example:
Router(config-cp)# service-policy input control-plane-policy |
Attaches a QoS service policy to filter and manage CP traffic on a specified line card before the aggregate CP policy is applied. • • Note |
Verifying Aggregate CP Services
To display information about the service policy attached to the control plane for aggregate CP services, perform the following optional steps.
SUMMARY STEPS
1. enable
2. show policy-map control-plane [all] [input [class class-name] | output [class class-name]]
DETAILED STEPS
|
Command or Action
|
Purpose
|
|
|---|---|---|
| Step 1 |
enable
Example:
Router> enable |
Enables privileged EXEC mode. • |
| Step 2 |
show policy-map control-plane [all]<!--
Example:
Router# show policy-map control-plane all |
Displays information about the control plane. • • • • |
Examples
The following example shows that the policy map TEST is associated with the control plane. This policy map polices traffic that matches the class map TEST, while allowing all other traffic (that matches the class map "class-default") to go through as is. (Table 1 describes the significant fields shown in the display.)
Router# show policy-map control-plane
Control Plane
Service-policy input:TEST
Class-map:TEST (match-all)
20 packets, 11280 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match:access-group 101
police:
8000 bps, 1500 limit, 1500 extended limit
conformed 15 packets, 6210 bytes; action:transmit
exceeded 5 packets, 5070 bytes; action:drop
violated 0 packets, 0 bytes; action:drop
conformed 0 bps, exceed 0 bps, violate 0 bps
Class-map:class-default (match-any)
105325 packets, 11415151 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match:any
Verifying Distributed CP Services
To display information about the service policy attached to the control plane to perform distributed CP services, perform the following optional steps.
SUMMARY STEPS
1. enable
2. show policy-map control-plane [all | slot slot-number] [input [class class-name] | output [class class-name]]
DETAILED STEPS
|
Command or Action
|
Purpose
|
|
|---|---|---|
| Step 1 |
enable
Example:
Router> enable |
Enables privileged EXEC mode. • |
| Step 2 |
show policy-map control-plane [all]
Example:
Router# show policy-map control-plane slot 2 |
Displays information about the service policy used to apply distributed CP services on the router. • • • • • |
Examples
The following example shows how to display information about the classes of CP traffic received from all interfaces on the line card in slot 1 to which the policy map TESTII is applied for distributed CP services. This policy map polices traffic that matches the traffic class TESTII, while allowing all other traffic (that matches the class map "class-default") to go through as is. (Table 1 describes the significant fields shown in the display.)
Router# show policy-map control-plane slot 1
Control Plane - slot 1
Service-policy input: TESTII (1048)
Class-map: TESTII (match-all) (1049/4)
0 packets, 0 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: protocol arp (1050)
police:
cir 8000 bps, bc 4470 bytes, be 4470 bytes
conformed 0 packets, 0 bytes; actions:
transmit
exceeded 0 packets, 0 bytes; actions:
drop
violated 0 packets, 0 bytes; actions:
drop
conformed 0 bps, exceed 0 bps, violate 0 bps
Class-map: class-default (match-any) (1052/0)
0 packets, 0 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: any (1053)
Configuration Examples for Control Plane Policing
This section contains examples that shows how to configure aggregate control plane services on both an input and an output interface:
•Configuring Control Plane Policing on Input Telnet Traffic: Example
•Configuring Control Plane Policing on Output ICMP Traffic: Example
Configuring Control Plane Policing on Input Telnet Traffic: Example
The following example shows how to apply a QoS policy for aggregate CP services to Telnet traffic received on the control plane. Trusted hosts with source addresses 10.1.1.1 and 10.1.1.2 forward Telnet packets to the control plane without constraint, while allowing all remaining Telnet packets to be policed at the specified rate:
<!---->! Allow 10.1.1.1 trusted host traffic.
Router(config)# access-list 140 deny tcp host 10.1.1.1 any eq telnet
! Allow <!---->10.1.1.2 trusted host traffic.
Router(config)# access-list 140 deny tcp host 10.1.1.2 any eq telnet
! Rate limit all other Telnet traffic.
Router(config)# access-list 140 permit tcp any any eq telnet
! Define class-map "telnet-class."
Router(config)# class-map telnet-class
Router(config-cmap)# match access-group 140
Router(config-cmap)# exit
Router(config)# policy-map control-plane-in
Router(config-pmap)# class telnet-class
Router(config-pmap-c)# police 80000 conform transmit exceed drop
Router(config-pmap-c)# exit
Router(config-pmap)# exit
! Define aggregate control plane service for the active Route Processor.
Router(config)# control-plane
Router(config-cp)# service-policy input control-plane-in
Router(config-cp)# exit
Configuring Control Plane Policing on Output ICMP Traffic: Example
The following example shows how to apply a QoS policy for aggregate CP services to Telnet traffic transmitted from the control plane. Trusted networks with source addresses 3.3.3.0 and 4.4.4.0 receive Internet Control Management Protocol (ICMP) port-unreachable responses without constraint, while allowing all remaining ICMP port-unreachable responses to be dropped:
! Allow 3.3.3.0 trusted network traffic.
Router(config)# access-list 141 deny icmp 3.3.3.0 0.0.0.255 any port-unreachable
! Allow 4.4.4.0 trusted network traffic.
Router(config)# access-list 141 deny icmp 4.4.4.0 0.0.0.255 any port-unreachable
! Rate limit all other ICMP traffic.
Router(config)# access-list 141 permit icmp any any port-unreachable
Router(config)# class-map icmp-class
Router(config-cmap)# match access-group 141
Router(config-cmap)# exit
Router(config)# policy-map control-plane-out
! Drop all traffic that matches the class "icmp-class."
Router(config-pmap)# class icmp-class
Router(config-pmap-c)# drop
Router(config-pmap-c)# exit
Router(config-pmap)# exit
Router(config)# control-plane
! Define aggregate control plane service for the active route processor.
Router(config-cp)# service-policy output control-plane-out
Router(config-cp)# exit
Additional References
The following sections provide references related to Control Plane Policing.
Related Documents
|
Related Topic
|
Document Title
|
|---|---|
| QoS information and configuration tasks |
Cisco IOS Quality of Service Solutions Configuration Guide, Release 12.3 |
| Additional QoS commands |
Cisco IOS Quality of Service Solutions Command Reference, Release 12.3T |
Standards
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Standards
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Title
|
|---|---|
| No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature. |
— |
MIBs
|
MIBs
|
MIBs Link
|
|---|---|
| • Note |
To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator, found at the following URL: http://www.cisco.com/go/mibs |
RFCs
|
RFCs
|
Title
|
|---|---|
| None |
— |
Technical Assistance
|
Description
|
Link
|
|---|---|
| The Cisco Technical Support website, containing 30,000 pages of searchable technical content, including links to products, technologies, solutions, technical tips, and tools. Registered Cisco.com users can log in from this page to access even more content. |
http://www.cisco.cisco.com/ techsupport |
Command Reference
This section documents only new and modified commands.
New Commands in Cisco IOS Release 12.2(18)S
•control-plane
•service-policy (control-plane)
•show policy-map control-plane
Modified Commands in Cisco IOS Release 12.3(4)T
•service-policy (control-plane)
•show policy-map control-plane
New Command in Cisco IOS Release 12.3(7)T
•service-policy (control-plane)
Modified Commands in Cisco IOS Release 12.0(30)S
•control-plane [slot slot-number]
• show policy-map control-plane [slot slot-number]
control-plane
To enter control-plane configuration mode and apply quality of service (QoS) policy to police traffic destined for the control plane using aggregate line card or distributed control plane (CP) services, use the control-plane command in global configuration mode.
control-plane [slot slot-number]
Syntax Description
| slot slot-number |
(Optional) Specifies the slot number of the line card to which you want to attach a QoS policy to perform distributed CP services. |
Defaults
No control plane service policies are defined.
Command Modes
Global configuration
Command History
|
Release
|
Modification
|
|---|---|
| 12.2(18)S |
This command was introduced. |
| 12.3(4)T |
This command was integrated into Cisco IOS Release 12.3(4)T. |
| 12.0(29)S |
This command was integrated into Cisco IOS Release 12.0(29)S. |
| 12.0(30)S |
The slot slot-number parameter was added to configure distributed CP services. |
| 12.2(18)SXD1 |
This command was integrated into Cisco IOS Release 12.2(18)SXD1. |
| 12.2(27)SBC |
This command was integrated into Cisco IOS Release 12.2(27)SBC. |
Usage Guidelines
After you enter the control-plane command, you can define aggregate and distributed control plane services for the route processor (RP). You can configure a service policy to police all traffic destined to the control plane:
•From all line cards on the router (aggregate CP services)
•From all interfaces on a line card (distributed CP services)
Aggregate CP services manage traffic destined for the control plane and received on the central switch engine from all line cards in the router. Distributed CP services manage CP traffic from interfaces on a specified line card before CP packets are forwarded to the central switch engine where aggregate CP services are applied. You can combine distributed and aggregate CP services to protect the control plane from DoS attacks and provide packet QoS.
Examples
The following example shows how to configure trusted hosts with source addresses 10.1.1.1 and 10.1.1.2 to forward Telnet packets to the control plane without constraint, while allowing all remaining Telnet packets to be policed at the specified rate. The QoS policy is then applied for aggregate CP services to all packets that are entering the control plane from all line cards in the router.
<!---->! Allow 10.1.1.1 trusted host traffic.
Router(config)# access-list 140 deny tcp host 10.1.1.1 any eq telnet
! Allow <!---->10.1.1.2 trusted host traffic.
Router(config)# access-list 140 deny tcp host 10.1.1.2 any eq telnet
! Rate limit all other Telnet traffic.
Router(config)# access-list 140 permit tcp any any eq telnet
! Define class-map "telnet-class."
Router(config)# class-map telnet-class
Router(config-cmap)# match access-group 140
Router(config-cmap)# exit
Router(config)# policy-map control-plane-in
Router(config-pmap)# class telnet-class
Router(config-pmap-c)# police 80000 conform transmit exceed drop
Router(config-pmap-c)# exit
Router(config-pmap)# exit
! Define aggregate control plane service for the active Route Processor.
Router(config)# control-plane
Router(config-cp)# service-policy input control-plane-in
Router(config-cp)# exit
The next example also shows how to configure trusted hosts with source addresses 10.1.1.1 and 10.1.1.2 to forward Telnet packets to the control plane without constraint, while allowing all remaining Telnet packets that enter through slot 1 to be policed at the specified rate. The QoS policy is applied for distributed CP services to all packets that enter through the interfaces on the line card in slot 1 and are destined for the control plane.
<!---->! Allow 10.1.1.1 trusted host traffic.
Router(config)# access-list 140 deny tcp host 10.1.1.1 any eq telnet
! Allow <!---->10.1.1.2 trusted host traffic.
Router(config)# access-list 140 deny tcp host 10.1.1.2 any eq telnet
! Rate limit all other Telnet traffic.
Router(config)# access-list 140 permit tcp any any eq telnet
! Define class-map "telnet-class."
Router(config)# class-map telnet-class
Router(config-cmap)# match access-group 140
Router(config-cmap)# exit
Router(config)# policy-map control-plane-in
Router(config-pmap)# class telnet-class
Router(config-pmap-c)# police 80000 conform transmit exceed drop
Router(config-pmap-c)# exit
Router(config-pmap)# exit
! Define aggregate control plane service for the active Route Processor.
Router(config)# control-plane slot 1
Router(config-cp)# service-policy input control-plane-in
Router(config-cp)# exit
Related Commands
|
Command
|
Description
|
|---|---|
| service-policy (control-plane) |
Attaches a policy map to the control plane for aggregate or distributed control plane services. |
| show policy-map control-plane |
Displays the configuration of a traffic class or all classes for the policy map attached to the control plane. |
service-policy (control-plane)
To attach a policy map to a control plane for aggregate or distributed control plane services, use the service-policy command in control-plane configuration mode. To remove a service policy from a control plane, use the no form of this command.
service-policy {input | output} policy-map-name
no service-policy {input | output} policy-map-name
Syntax Description
| input |
Applies the specified service policy to packets that are entering the control plane. |
| output |
Applies the specified service policy to packets that are exiting the control plane, and enables the router to silently discard packets. The output keyword is: • – – • • |
| policy-map-name |
Name of the service policy map (created using the policy-map command) to be attached. The name can be a maximum of 40 alphanumeric characters. |
Defaults
No service policy is specified.
Command Modes
Control-plane configuration
Command History
|
Release
|
Modification
|
|---|---|
| 12.2(18)S |
This command was introduced. |
| 12.3(4)T |
This command was integrated into Cisco IOS Release 12.3(4)T, and support for the output keyword was added. |
| 12.0(29)S |
This command was integrated into Cisco IOS Release 12.0(29)S. |
| 12.2(18)SXD1 |
This command was integrated into Cisco IOS Release 12.2(18)SXD1. |
| 12.2(25)S |
Support for the output keyword was integrated into Cisco IOS Release 12.2(25)S. |
| 12.2(27)SBC |
This command was integrated into Cisco IOS Release 12.2(27)SBC. |
Usage Guidelines
After entering the control-plane command, use the service-policy command to configure a quality of service (QoS) policy. This policy is attached to the control plane interface for aggregate or distributed control plane services, and controls the number or rate of packets sent to the process level.
When you configure output policing on control-plane traffic, using the service-policy output policy-map-name command, a router is automatically enabled to silently discard packets. Note that output policing is supported as follows:
•Supported only in:
–Cisco IOS Release 12.2(25)S and later Cisco IOS 12.2S releases
–Cisco IOS Release 12.3(4)T and later Cisco IOS 12.3T releases.
•Not supported for attaching a QoS policy for distributed control-plane services.
•Not supported on the Cisco 7500 series and Cisco 10720 Internet router.
The service-policy output command configures output policing, which is performed in silent mode to silently discard packets exiting from the control plane according to the attached QoS policy. Silent mode allows a router that is running Cisco IOS software to operate without sending any system messages. If a packet that is exiting from the control plane is discarded for output policing, you do not receive an error message.
When the Control Plane Policing feature is configured for output traffic, error messages are not generated in the following cases:
•Traffic that is being transmitted to a port to which the router is not listening
•A connection to a legitimate address and port that is rejected because of a malformed request
Examples
The following example shows how to configure trusted hosts with source addresses 10.1.1.1 and 10.1.1.2 to forward Telnet packets to the control plane without constraint, while allowing all remaining Telnet packets to be policed at the specified rate:
<!---->! Allow 10.1.1.1 trusted host traffic.
Router(config)# access-list 140 deny tcp host 10.1.1.1 any eq telnet
! Allow <!---->10.1.1.2 trusted host traffic.
Router(config)# access-list 140 deny tcp host 10.1.1.2 any eq telnet
! Rate limit all other Telnet traffic.
Router(config)# access-list 140 permit tcp any any eq telnet
! Define class-map "telnet-class."
Router(config)# class-map telnet-class
Router(config-cmap)# match access-group 140
Router(config-cmap)# exit
Router(config)# policy-map control-plane-policy
Router(config-pmap)# class telnet-class
Router(config-pmap-c)# police 80000 conform transmit exceed drop
Router(config-pmap-c)# exit
Router(config-pmap)# exit
! Define aggregate control plane service for the active Route Processor.
Router(config)# control-plane
Router(config-cp)# service-policy input control-plane-policy
Router(config-cp)# exit
The next example shows how to configure trusted networks with source addresses 3.3.3.0 and 4.4.4.0 to receive Internet Control Message Protocol (ICMP) port-unreachable responses without constraint, while allowing all remaining ICMP port-unreachable to be dropped:
! Allow 3.3.3.0 trusted network traffic.
Router(config)# access-list 141 deny icmp host 3.3.3.0 0.0.0.255 any port-unreachable
! Allow 4.4.4.0 trusted network traffic.
Router(config)# access-list 141 deny icmp host 4.4.4.0 0.0.0.255 any port-unreachable
! Rate limit all other ICMP traffic.
Router(config)# access-list 141 permit icmp any any port-unreachable
Router(config)# class-map icmp-class
Router(config-cmap)# match access-group 141
Router(config-cmap)# exit
Router(config)# policy-map control-plane-out-policy
! Drop all traffic that matches the class "icmp-class."
Router(config-pmap)# class icmp-class
Router(config-pmap-c)# drop
Router(config-pmap-c)# exit
Router(config-pmap)# exit
Router(config)# control-plane
! Define aggregate control plane service for the active route processor.
Router(config-cp)# service-policy output control-plane-policy
Router(config-cp)# exit
Related Commands
|
Command
|
Description
|
|---|---|
| control-plane |
Enters control-plane configuration mode to apply a QoS policy to police traffic destined for the control plane. |
| policy-map |
Creates or modifies a quality-of- service policy that can be attached to one or more interfaces. |
| show policy-map control-plane |
Displays the configuration of a traffic class or all classes for the policy map attached to the control plane. |
show policy-map control-plane
To display the configuration and statistics for a traffic class or all traffic classes in the policy maps attached to the control plane for aggregate or distributed control plane services, use the show policy-map control-plane command in privileged EXEC mode.
show policy-map control-plane [all | slot slot-number] [input [class class-name] | output | [class class-name]]
Syntax Description
| all |
(Optional) Displays information about all QoS policies used in aggregate and distributed CP services. |
| slot slot-number |
(Optional) Displays information about the QoS policy used to perform distributed CP services on the specified line card. |
| input |
(Optional) Displays statistics for the attached input policy. |
| output |
(Optional) Displays statistics for the attached output policy. Note |
| class class-name |
(Optional) Name of the traffic class whose configuration and statistics are displayed. |
Command Modes
Privileged EXEC
Command History
|
Release
|
Modification
|
|---|---|
| 12.2(18)S |
This command was introduced. |
| 12.3(4)T |
This command was integrated into Cisco IOS Release 12.3(4)T, and support for the output keyword was added. |
| 12.0(29)S |
This command was integrated into Cisco IOS Release 12.0(29)S |
| 12.2(18)SXD1 |
This command was integrated into Cisco IOS Release 12.2(18)SXD1. |
| 12.0(30)S |
Support for the slot slot-number parameter was added. |
| 12.2(25)S |
Support for the output keyword was integrated into Cisco IOS Release 12.2(25)S. |
Usage Guidelines
The show policy-map control-plane command displays information for aggregate and distributed control-plane services, which manage the number or rate of CP packets sent to the process level of the RP.
Information for distributed control-plane service is displayed for a specified line card. Distributed CP services are performed on a line card's distributed switch engine and manage CP traffic sent from all interfaces on the line card to the route processor, where aggregate CP services (for CP packets received from all line cards on the router) are performed.
Examples
The following example shows that the policy map TEST is associated with the control plane. This policy map polices traffic that matches the class-map TEST, while allowing all other traffic (that matches the class-map "class-default") to go through as is. Table 1 describes the significant fields shown in the command output.
Router# show policy-map control-plane
Control Plane
Service-policy input:TEST
Class-map:TEST (match-all)
20 packets, 11280 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match:access-group 101
police:
8000 bps, 1500 limit, 1500 extended limit
conformed 15 packets, 6210 bytes; action:transmit
exceeded 5 packets, 5070 bytes; action:drop
violated 0 packets, 0 bytes; action:drop
conformed 0 bps, exceed 0 bps, violate 0 bps
Class-map:class-default (match-any)
105325 packets, 11415151 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match:any
|
Field
|
Description
|
|---|---|
| Fields Associated with Classes or Service Policies |
|
| Service-policy input |
Name of the input service policy that is applied to the control plane. (If configured, this field will also show the output service policy.) |
| Class-map |
Class of traffic being displayed. Traffic is displayed for each configured class. The choice for implementing class matches (for example, match-all or match-any) can also appear next to the traffic class. |
| offered rate |
Rate, in kbps, at which packets are coming into the class. |
| drop rate |
Rate, in kbps, at which are dropped from the class. The drop rate is calculated by subtracting the number of successfully transmitted packets from the offered rate. |
| Match |
Match criteria for the specified class of traffic. For more information about the variety of match criteria options available, refer to the chapter "Configuring the Modular Quality of Service Command-Line Interface" in the Cisco IOS Quality of Service Solutions Configuration Guide. |
| Fields Associated with Traffic Policing |
|
| police |
Indicates that the police command has been configured to enable traffic policing. |
| conformed |
Displays the action to be taken on packets conforming to a specified rate. Displays the number of packets and bytes on which the action was taken. |
| exceeded |
Displays the action to be taken on packets exceeding a specified rate. Displays the number of packets and bytes on which the action was taken. |
| violated |
Displays the action to be taken on packets violating a specified rate. Displays the number of packets and bytes on which the action was taken. |
Related Commands
|
Command
|
Description
|
|---|---|
| control-plane |
Enters control-plane configuration mode to apply a QoS policy to police traffic destined for the control plane. |
| service-policy (control-plane) |
Attaches a policy map to the control plane for aggregate or distributed control plane services. |