Catalyst 4500 Series Switch Software Configuration Guide, 12.2(53)SG

Configuring Control Plane Policing

This chapter contains information on how to protect your Catalyst 4000 family switch using control plane policing (CoPP). The information covered in this chapter is unique to the Catalyst 4500 series switches, and it supplements the network security information and procedures in Chapter 47 "Configuring Network Security with ACLs." This information also supplements the network security information and procedures in these publications:

•Cisco IOS Security Configuration Guide, Cisco IOS Release 12.4, at this URL:

http://www.cisco.com/en/US/docs/ios/security/configuration/guide/12_4/sec_12_4_book.html

•Cisco IOS Security Command Reference, Cisco IOS Release 12.4, at this URL:

http://www.cisco.com/en/US/docs/ios/security/command/reference/sec_book.html

This chapter includes the following major sections:

•Understanding How Control Plane Policing Works

•Caveats for Control Plane Policing

•CoPP Default Configuration

•Configuring CoPP

•CoPP Configuration Guidelines and Restrictions

•Monitoring CoPP

Note For complete syntax and usage information for the switch commands used in this chapter, see the Cisco Catalyst 4500 Series Switch Command Reference and related publications at this location:

http://www.cisco.com/en/US/products/hw/switches/ps4324/index.html

If the command is not found in the Cisco Catalyst 4500 Command Reference, you can locate it in the larger Cisco IOS library. Refer to the Catalyst 4500 Series Switch Cisco IOS Command Reference and related publications at this location:

http://www.cisco.com/en/US/products/ps6350/index.html

Understanding How Control Plane Policing Works

The control plane policing (CoPP) feature increases security on the Catalyst 4000 family switch by protecting the CPU from unnecessary or DoS traffic and giving priority to important control plane and management traffic. The classification TCAM and QoS policers provide CoPP hardware support.

Note CoPP is supported on the following: Classic Series supervisor engines and switches beginning with Cisco IOS Release 12.2(31)SG; Supervisor 6-E and Catalyst 4900M beginning with Cisco IOS Release 12.2(50)SG; and Supervisor 6L-E in Cisco IOS Release 12.2(52)X0.

The traffic managed by the CPU is divided into three functional components or planes:

•Data plane

•Management plane

•Control plane

You can use CoPP to protect most of the CPU bound traffic and ensure routing stability, reachability and packet delivery. Most importantly, CoPP is often used to protect the CPU from the DoS attack. There is a list of pre-defined ACLs matching a selected set of Layer 2 and Layer 3 control plane packets. You can define your preferred policing parameters to each of these control packets but you cannot modify the matching criteria of these pre-defined ACLs. Following is the list of pre-defined ACLs:

For the Data Plane and Management Plane traffic, you can define your own ACLs to match the traffic class that you want to police.

CoPP uses MQC to define traffic classification criteria and to specify the configurable policy actions for the classified traffic. MQC uses class maps to define packets for a particular traffic class. After you have classified the traffic, you can create policy maps to enforce policy actions for the identified traffic. The control-plane global configuration command allows the CoPP service policy to be directly attached to the control plane.

The only policy-map that you can attach to the control-plane is system-cpp-policy. It must contain the pre-defined class-maps in the pre-defined order at the beginning of the policy map. The best way to create the system-cpp-policy policy-map is through the global macro system-cpp.

The system-cpp-policy contains the pre-defined class maps for the control plane traffic. The names of all system defined CoPP class maps and their matching ACLs contain the prefix "system-cpp-". By default, no action is specified for each traffic class. You can define your own class maps matching CPU bound data plane and management plane traffic. You can add your defined class maps to the system-cpp-policy policy-map.

Caveats for Control Plane Policing

•Port Security might cancel its effect for non-IP control packets.

Although Source MAC Learning on the Catalyst 4500 series switch is performed in software, learning of source MAC addresses from control packets (e.g.: IEEE BPDU/CDP/SSTP BPDU/GARP/etc) is disallowed. Once you configure Port Security on a port where you expect to receive a high rate of such (possibly rogue) control packets, the system generates a copy of the packet to the CPU (until the source address is learned, how Port Security is implemented), rather than forward it.

The current architecture of the Catalyst 4500 switching engine does not allow you to apply policing on the copy of packets sent to the CPU; policing can only be applied on packets that are forwarded to CPU. So, copies of packets are sent to the CPU at the rate control packets arrive and Port Security is not triggered because learning from control packets is disallowed. Furthermore, policing will not be applied because the packet copy, not the original, is sent to the CPU.

•As of Cisco IOS Release 12.2(31)SGA1, the GARP class is no longer part of the CoPP. (Due to the fix associated with CSCsg08775, even though the system-cpp-garp-range entry still appears in the CPP configuration, it is merely idling and will be removed in future releases.) Henceforward, you can manipulate GARP traffic with user ACLs and QoS. If you want to protect CPU against GARP packets, you also can "police down" GARP packets using CoPP after you define the user class for the GARP packet. (This is now possible because GARP is no longer part of the Static CAM area.)

Due to tight integration of CPP implementation between IOS and platform code, an error message will always appear during boot-up and CPP will not be applied when downgrading IOS software from a version where this caveat is integrated to a previous release (where this fix is not present):

%Invalid control plane policy-map; Please unconfigure policy-map attached to 
control-plane, and associated class-maps, and execute config command "macro global 
apply system-cpp" error: failed to install policy map system-cpp-policy

As a workaround do the following:

1. Back-up your configuration when performing software downgrading.

2. Remove all CPP entries manually from the config and then re-appy the
macro global apply system-cpp command.

There should be no problem associated with this caveat while upgrading between releases.

•ARP policing is not supported on either Classic series supervisor engines or fixed configuration switches. It is, however, supported on the Supervisor Engine 6-E and the Catalyst 4900M switch.

•You cannot remove a macro populated class from the list of classes within a control plane policy.

•Prior to Cisco IOS Release 12.2(50)SG, on switches with Supervisor Engines V, V-10GE and earlier, class-map hit statistics on a user defined class-map in system-cpp-policy are not updated properly. With Cisco IOS Release 12.2(50)SG, the hit statistics for user-defined class-map in the system-cpp-policy are updated properly. However, in per-vlan capture mode, the hit stats for system defined in system-cpp-policy are not updated. In the global capture mode, hit stats for all class-maps (user-defined and system-defined) in the system-cpp-policy are updated properly.

CoPP Default Configuration

CoPP is disabled by default.

Configuring CoPP

This section includes the following tasks:

•Configure CoPP for Control Plane Traffic

•Configure CoPP for Data Plane and Management Plane Traffic

Configure CoPP for Control Plane Traffic

To configure CoPP for Control Plane traffic, perform this task:

Switch(config-pmap)# class 
{system-cpp-dot1x | system-cpp-bpdu-range | 
system-cpp-cdp | service | system-cpp-sstp 
| system-cpp-cgmp | system-cpp-ospf | 
system-cpp-igmp | system-cpp-pim | 
system-cpp-all-systems-on-subnet | 
system-cpp-all-routers-on-subnet | 
system-cpp-ripv2 | system-cpp-hsrpv2 | 
system-cpp-ip-mcast-linklocal | 
system-cpp-dhcp-cs | system-cpp-dhcp-sc | 
system-cpp-dhcp-ss} 

Switch(config-pmap-c)# police [aggregate 
name] rate burst [conform-action {drop | 
transmit}] [{exceed-action {drop | 
transmit}}]}

The following example shows how to police CDP packets:

Switch# config terminal

Enter configuration commands, one per line.  End with CNTL/Z.

Switch(config)# qos

Switch(config)# macro global apply system-cpp

Switch(config)# policy-map system-cpp-policy

Switch(config-pmap)# class system-cpp-cdp

Switch(config-pmap-c)# police 32000 1000 conform-action transmit exceed-action drop 
Switch(config-pmap-c)# end

Switch# show policy-map system-cpp-policy

  Policy Map system-cpp-policy

    Class system-cpp-dot1x

    Class system-cpp-bpdu-range

*    Class system-cpp-cdp

      police 32000 bps 1000 byte conform-action transmit exceed-action drop *

    Class system-cpp-sstp

    Class system-cpp-cgmp

    Class system-cpp-ospf

    Class system-cpp-hsrpv2

    Class system-cpp-igmp

    Class system-cpp-pim

    Class system-cpp-all-systems-on-subnet

    Class system-cpp-all-routers-on-subnet

    Class system-cpp-ripv2

    Class system-cpp-ip-mcast-linklocal

    Class system-cpp-dhcp-cs

    Class system-cpp-dhcp-sc

    Class system-cpp-dhcp-ss

Switch#

Configure CoPP for Data Plane and Management Plane Traffic

To configure CoPP for Data Plane and Management Plane traffic, perform this task:

For an ip access list, issue

Switch(config-ext-nacl)#{permit|deny} 
{protocol} source {source-wildcard} 
destination {destination-wildcard}

For a mac access list, issue

Switch(config-ext-macl)#{permit|deny} 
source {source-wildcard} destination 
{destination-wildcard} [protocol-family]

OR

Switch(config)# access-list 
{access-list-name} {permit | deny} 
{type-code wild-mask | address mask}

Switch(config)# class-map 
{traffic-class-name}  
 
Switch(config-cmap)# match access-group 
{access-list-number | name 
{access-list-name}}

Switch(config-cmap)# exit

Switch(config)# policy-map 
system-cpp-policy

 
Switch(config-pmap)# class <class-map-name>  
 
Switch(config-pmap-c)# police 
[aggregate name] rate burst 
[conform-action {drop | transmit}] 
[{exceed-action {drop | transmit}}]

Switch(config)# end

Switch# show policy-map system-cpp-policy

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 specific rate (this example assumes the global qos is enabled and the system-cpp-policy policy-map has been created):

Switch# config terminal

Enter configuration commands, one per line.  End with CNTL/Z.

Switch(config)# qos

Switch(config)# macro global apply system-cpp

! Allow 10.1.1.1 trusted host traffic.

Switch(config)# access-list 140 deny tcp host 10.1.1.1 any eq telnet

! Allow 10.1.1.2 trusted host traffic.

Switch(config)# access-list 140 deny tcp host 10.1.1.2 any eq telnet

! Rate limit all other Telnet traffic.

Switch(config)# access-list 140 permit tcp any any eq telnet

! Define class-map "telnet-class."

Switch(config)# class-map telnet-class

Switch(config-cmap)# match access-group 140

Switch(config-cmap)# exit

! Add the class-map "telnet-class" to "system-cpp-policy" and define ! the proper action 
Switch(config)# policy-map system-cpp-policy

Switch(config-pmap)# class telnet-class

Switch(config-pmap-c)# police 80000 1000 conform transmit exceed drop 
Switch(config-pmap-c)# exit

Switch(config-pmap)# exit

! Verify the above configuration steps

Switch# show policy-map system-cpp-policy

  Policy Map system-cpp-policy

    Class system-cpp-dot1x

    Class system-cpp-bpdu-range

    Class system-cpp-cdp

      police 32000 bps 1000 byte conform-action transmit exceed-action drop

    Class system-cpp-sstp

    Class system-cpp-cgmp

    Class system-cpp-ospf

    Class system-cpp-hsrpv2

    Class system-cpp-igmp

    Class system-cpp-pim

    Class system-cpp-all-systems-on-subnet

    Class system-cpp-all-routers-on-subnet

    Class system-cpp-ripv2

    Class system-cpp-ip-mcast-linklocal

    Class system-cpp-dhcp-cs

    Class system-cpp-dhcp-sc

    Class system-cpp-dhcp-ss

*    Class telnet-class

      police 8000 bps 1000 byte conform-action drop exceed-action drop

CoPP Configuration Guidelines and Restrictions

When configuring CoPP, follow these guidelines and restrictions:

•Only ingress CoPP is supported. So only input keyword is supported in control-plane related CLIs.

•Use the system defined class maps for policing control plane traffic.

•Control plane traffic can be policed only using CoPP. Traffic cannot be policed at the input interface or VLAN even though a policy-map containing the control-plane traffic is accepted when the policy-map is attached to an interface or VLAN.

•System-defined class maps cannot be used in policy-maps for regular QoS.

•Use ACLs and class-maps to identify data plane and management plane traffic that are handled by CPU. User-defined class maps should be added to the system-cpp-policy policy-map for CoPP.

•The policy-map named system-cpp-policy is dedicated for CoPP.

•The default system-cpp-policy map does not define actions for the system-defined class maps, which means no policing.

•The only action supported in system-cpp-policy policy-map is police.

•Do not use the log keyword in the CoPP policy ACLs.

•Both MAC and IP ACLs can be used to define data plane and management plane traffic classes. But if a packet also matches a pre-defined ACL for the control plane traffic, the police action (or no police action) of the control plane class will be taken as the control plane classes appear above user-defined classes in the service policy. This is the same MQC semantic.

•The exceeding action policed-dscp-transmit is not supported for CoPP.

•CoPP is not enabled unless the global QoS is enabled and police action is specified.

Monitoring CoPP

You can enter the show policy-map control-plane command for developing site-specific policies, monitoring statistics for the control plane policy, and troubleshooting CoPP. This command displays dynamic information about the actual policy applied including rate information and the number of bytes (and packets) that conformed or exceeded the configured policies both in hardware and in software.

The output of the show policy-map control-plane command is as follows:

Switch# show policy-map control-plane

Control Plane

Service-policy input: system-cpp-policy

    Class-map: system-cpp-dot1x (match-all)

      0 packets

      Match: access-group name system-cpp-dot1x

    Class-map: system-cpp-bpdu-range (match-all)

      0 packets

      Match: access-group name system-cpp-bpdu-range

*    Class-map: system-cpp-cdp (match-all)

      160 packets

      Match: access-group name system-cpp-cdp

**      police: Per-interface

        Conform: 22960 bytes Exceed: 0 bytes

*

    Class-map: system-cpp-sstp (match-all)

      0 packets

      Match: access-group name system-cpp-sstp

    Class-map: system-cpp-cgmp (match-all)

      0 packets

      Match: access-group name system-cpp-cgmp

    Class-map: system-cpp-hsrpv2 (match-all)

      0 packets

      Match: access-group name system-cpp-hsrpv2

    Class-map: system-cpp-ospf (match-all)

      0 packets

      Match: access-group name system-cpp-ospf

    Class-map: system-cpp-igmp (match-all)

      0 packets

      Match: access-group name system-cpp-igmp

    Class-map: system-cpp-pim (match-all)

      0 packets

      Match: access-group name system-cpp-pim

    Class-map: system-cpp-all-systems-on-subnet (match-all)

      0 packets

      Match: access-group name system-cpp-all-systems-on-subnet

    Class-map: system-cpp-all-routers-on-subnet (match-all)

      0 packets

      Match: access-group name system-cpp-all-routers-on-subnet

    Class-map: system-cpp-ripv2 (match-all)

      0 packets

      Match: access-group name system-cpp-ripv2

    Class-map: system-cpp-ip-mcast-linklocal (match-all)

      0 packets

      Match: access-group name system-cpp-ip-mcast-linklocal

    Class-map: system-cpp-dhcp-cs (match-all)

      83 packets

      Match: access-group name system-cpp-dhcp-cs

    Class-map: system-cpp-dhcp-sc (match-all)

      0 packets

      Match: access-group name system-cpp-dhcp-sc

    Class-map: system-cpp-dhcp-ss (match-all)

      0 packets

      Match: access-group name system-cpp-dhcp-ss

*    Class-map: telnet-class (match-all)

      0 packets

      Match: access-group 140

**      police: Per-interface

        Conform: 0 bytes Exceed: 0 bytes*

    Class-map: class-default (match-any)

      0 packets

      Match: any

        0 packets

Switch#

To clear the counters on the control-plane, enter the clear control-plane * command:

Switch# clear control-plane *

Switch#

To display all the CoPP access list information, enter the show access-lists command:

Switch# show access-lists

Extended IP access list system-cpp-all-routers-on-subnet

10 permit ip any host 224.0.0.2

Extended IP access list system-cpp-all-systems-on-subnet

10 permit ip any host 224.0.0.1

Extended IP access list system-cpp-dhcp-cs

10 permit udp any eq bootpc any eq bootps Extended IP access list 

system-cpp-dhcp-sc

10 permit udp any eq bootps any eq bootpc Extended IP access list 

system-cpp-dhcp-ss

10 permit udp any eq bootps any eq bootps Extended IP access list 

system-cpp-igmp

10 permit igmp any 224.0.0.0 31.255.255.255 Extended IP access list 

system-cpp-ip-mcast-linklocal

10 permit ip any 224.0.0.0 0.0.0.255 Extended IP access list 

system-cpp-ospf

10 permit ospf any 224.0.0.0 0.0.0.255 Extended IP access list 

system-cpp-pim

10 permit pim any 224.0.0.0 0.0.0.255 Extended IP access list 

system-cpp-ripv2

10 permit ip any host 224.0.0.9

Extended MAC access list system-cpp-bpdu-range

permit any 0180.c200.0000 0000.0000.000f Extended MAC access list 

system-cpp-cdp

permit any host 0100.0ccc.cccc

Extended MAC access list system-cpp-cgmp

permit any host 0100.0cdd.dddd

Extended MAC access list system-cpp-dot1x

permit any host 0180.c200.0003

system-cpp-sstp

permit any host 0100.0ccc.cccd

To display one CoPP access list, enter the show access-lists system-cpp-cdp command:

Switch# show access-list system-cpp-cdp

Extended MAC access list system-cpp-cdp

permit any host 0100.0ccc.cccc

Switch#