Source-Based Rate Limit

The Source-Based Rate Limit (SBRL) feature prevents congestion of packets on the forwarding processor (FP) to the Route Processor (RP) interface, which can be caused by denial of service (DoS) attacks directed at the Cisco CMTS or by faulty hardware.

Your software release may not support all the features that are documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. The Feature Information Table at the end of this document provides information about the documented features and lists the releases in which each feature is supported.

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Contents

Hardware Compatibility Matrix for the Cisco cBR Series Routers


Note
The hardware components that are introduced in a given Cisco IOS-XE Release are supported in all subsequent releases unless otherwise specified.
Table 1. Hardware Compatibility Matrix for the Cisco cBR Series Routers

Cisco CMTS Platform

Processor Engine

Interface Cards

Cisco cBR-8 Converged Broadband Router

Cisco IOS-XE Release 16.5.1 and Later Releases

Cisco cBR-8 Supervisor:

  • PID—CBR-SUP-250G

  • PID—CBR-CCAP-SUP-160G

Cisco IOS-XE Release 16.5.1 and Later Releases

Cisco cBR-8 CCAP Line Cards:

  • PID—CBR-LC-8D30-16U30

  • PID—CBR-LC-8D31-16U30

  • PID—CBR-RF-PIC

  • PID—CBR-RF-PROT-PIC

  • PID—CBR-CCAP-LC-40G

  • PID—CBR-CCAP-LC-40G-R

  • PID—CBR-CCAP-LC-G2-R

  • PID—CBR-SUP-8X10G-PIC

  • PID—CBR-2X100G-PIC

Digital PICs:

  • PID—CBR-DPIC-8X10G

  • PID—CBR-DPIC-2X100G

Cisco cBR-8 Downstream PHY Module:

  • PID—CBR-D31-DS-MOD

Cisco cBR-8 Upstream PHY Modules:

  • PID—CBR-D31-US-MOD

Prerequisites for Source-Based Rate Limit

  • You must configure Control-Plane Policing (CoPP) for WAN-side SBRL.

Restrictions for Source-Based Rate Limit

  • WAN-IP and Subscriber MAC address entities are identified using a hash, and hash collisions can occur between two (or more) entities.

  • On the WAN-side there is no special processing for hash collisions. Sources that hash-collide are rate-limited as if they are the same source.

  • The QOS group 99 is reserved for SBRL and cannot be used for other class maps.

Information About Source-Based Rate Limit

Source-Based Rate Limit (SBRL) feature operates on the punt path in CPP. SBRL identifies and rate-limits the packet streams that can overload the punt path or RP.

Punted packets are sent from the FP to the RP through the FP-to-RP queues. Denial of service (DoS) can occur when:

  • The FP-to-RP queues are congested

  • The RP cannot process punted packets fast enough

In both cases, the valid punted packets are not processed properly. These situations can be caused deliberately by DoS attacks or by faulty external hardware.

Packet streams identified by SBRL are rate-limited according to configured parameters. Rate-limiting occurs in CPP before the packets reach the FP-to-RP queues. This protects the RP, and also allows other valid punted packets to reach the RP.

SBRL has a separate configuration for the WAN-side and the subscriber-side. WAN-side SBRL is disabled by default. Subscriber-side SBRL has default settings.

WAN-Side Source-Based Rate Limit

WAN-side SBRL uses Control Plane Policing (CoPP). CoPP specifies the WAN-side packet streams that are directed for SBRL. Both trusted and untrusted sites can be specified using CoPP. Using CoPP, you can specify unlimited trusted sites. Access control list (ACL) is used to specify the trusted sites.

Subscriber-Side Source-Based Rate Limit

All subscriber-side punts are processed by subscriber-side SBRL. Note that the CoPP processes all punted packets, but there is no dependency between CoPP and subscriber-side SBRL.

How to Configure Source-Based Rate Limit

This section contains the following:

Configuring WAN-Side Source-Based Rate Limit

You must enable WAN-side SBRL in two parts:

  1. Configure Control Plane Policing (CoPP) to specify which packets are subject to SBRL.

  2. Configure WAN-side SBRL to set the rate-limiting parameters for the specified punt-causes.

In the CoPP policy map, the special action set qos-group 99 denotes that the packets matching a particular class are subject to WAN-side SBRL. This means that the QOS group 99 is globally reserved for SBRL, and must not be used in other policy-maps.

Packets matching a class without set qos-group 99 bypass WAN-side SBRL. This means that CoPP is also used to specify trusted traffic streams that are not subject to WAN-side SBRL.

All punted packets are subject to CoPP. So, you must ensure that subscriber-side traffic does not match a trusted class.

WAN-side SBRL identifies traffic streams by hashing the punt cause, VRF index, and source IP address. This value is used as the index for rate-limiting. The router does not perform special processing for hash collisions, so hash-colliding streams are treated as if they are from the same stream.

By default, WAN-side SBRL is disabled.

Restrictions

  • All the punted packets are subject to CoPP and punt-policing.

This section contains the following:

Configuring Control Plane Policing

Punted packets matching the trusted class bypass WAN-side SBRL. The rest of the WAN-side punts are sent to WAN-side SBRL.


Note

The following example shows a simple trusted class.

Procedure
  Command or Action Purpose
Step 1

enable

Example:
Router> enable

Enables privileged EXEC mode.

  • Enter your password, if prompted.

Step 2

configure terminal

Example:
Router# configure terminal

Enters global configuration mode.

Step 3

access-list access-list-number permit protocol {any | host {address | name}} {any | host {address | name}} tos tos

Example:
Router(config)# access-list 130 permit ip 192.168.1.10 0.0.0.0 192.168.1.11 0.0.0.0 tos 4

Configures an access list for filtering frames by protocol type.

Note 

Since all the punted packets are subject to CoPP, you must ensure that subscriber-side traffic does not match a trusted class.

Step 4

class-map class-map-name

Example:
Router(config)#  class-map match-all sbrl_v4_trusted

Creates a class-map and enters QoS class-map configuration mode.

Step 5

match access-group access-list-index

Example:
Router(config-cmap)# match access-group 130

Specifies access groups to apply to an identity policy. The range of is from 1 to 2799.

Step 6

exit

Example:
Router(config-cmap)# exit

Exits QoS class-map configuration mode and returns to global configuration mode.

Step 7

policy-map policy-map-name

Example:
Router(config)# policy-map copp_policy

Specifies a service policy and enters QoS policy-map configuration mode.

Step 8

class class-map-name

Example:
Router(config)# class sbrl_v4_trusted

Enters QoS policy-map class configuration mode.

Step 9

police rate units pps conform-action action exceed-action action

Example:
Router(config-pmap-c)#  police rate 1000 pps conform-action transmit exceed-action transmit

Polices traffic destined for the control plane at a specified rate.

Note 

The rate is irrelevant if both the configured actions are transmit.

Step 10

exit

Example:
Router(config-pmap-c)# exit

Exits policy-map class police configuration mode

Step 11

class class-default

Example:
Router(config-pmap)# class class-default

Specifies the action to take on the packets that do not match any other class in the policy map.

Step 12

set qos-group 99

Example:
Router(config-pmap-c)# set qos-group 99

Enables WAN-side SBRL for the packets that match this class.

Step 13

exit

Example:
Router(config-pmap-c)# exit

Exits policy-map class configuration mode

Step 14

exit

Example:
Router(config-pmap)# exit

Exits policy-map configuration mode

Step 15

control-plane [host | transit | cef-exception]

Example:
Router(config)# control-plane

Associates or modifies attributes (such as a service policy) that are associated with the control plane of the router and enters control plane configuration mode.

Step 16

service-policy {input | output} policy-map-name

Example:
Router(config-cp)# service-policy input copp_policy

Attaches a policy map to a control plane.

Step 17

end

Example:
Router(config-cp)# end

Exits control plane configuration mode and returns to privileged EXEC mode.

Enabling WAN-Side Source-Based Rate Limit

Procedure
  Command or Action Purpose
Step 1

enable

Example:
Router> enable

Enables privileged EXEC mode.

  • Enter your password, if prompted.

Step 2

configure terminal

Example:
Router# configure terminal

Enters global configuration mode.

Step 3

platform punt-sbrl wan punt-cause punt-cause rate-per-1-sec rate

Example:
Router(config)# platform punt-sbrl wan punt-cause 10 rate-per-1-sec 4

Configures WAN-side rate limit.

  • punt-cause punt-cause —Specifies the punt-cause value in number 1 to 107 or string.

  • rate-per-1-sec rate —Specifies the rate in packets per second. The range is from 1 to 256, specified in powers-of-2.

Configuring WAN-Side Quarantine

The WAN-side quarantine extends the WAN-side SBRL configuration. When a traffic stream enters quarantine, all punted packets in the stream are dropped for the configured period.

Procedure
  Command or Action Purpose
Step 1

enable

Example:
Router> enable

Enables privileged EXEC mode.

  • Enter your password, if prompted.

Step 2

configure terminal

Example:
Router# configure terminal

Enters global configuration mode.

Step 3

platform punt-sbrl wan punt-cause punt-cause rate-per-1-sec rate quarantine-time time burst-factor burst-factor

Example:
Router(config)# platform punt-sbrl wan punt-cause 10 rate-per-1-sec 4 quarantine-time 10 burst-factor 500

Configures quarantine for the WAN-side packet stream.

  • punt-cause punt-cause —Specifies the punt-cause value in number 1 to 107 or string.

  • rate-per-1-sec rate —Specifies the rate limit in packets per second. The range is from 1 to 256, specified in powers-of-2.

  • quarantine-time time —Specifies the quarantine time, in minutes. The range is from 1 to 60.

  • burst-factor burst-factor—Specifies the burst-factor, in number of packets. The range is from 50 to 1000.

Example

When (burst-factor x rate) packets arrive at a rate faster than rate, the packet stream enters quarantine.

For example, during a DoS attack, when the following occurs:

  • Punted packets from a WAN-side source are arrive at 100 packets per second.

  • WAN-side SBRL is configured with a rate of 4 packets per second, quarantine time of 10 minutes, and burst-factor of 500 packets.

The packet rate is significantly higher than the configured rate. Therefore, when 2000 (4 x 500) packets have arrived, the packet stream enters into quarantine. Quarantine is activated at 20 seconds (2000 packets per 100 packets per second), and all punted packets from the stream are dropped for 10 minutes. After 10 minutes, the quarantine is deactivated.

The quarantine calculations restart immediately. So, if the scanning attack is continuous, quarantine is reactivated after the next 20 seconds.

Configuring Subscriber-Side Source-Based Rate Limit

Restrictions

  • All punted packets are subject to CoPP and punt-policing.

  • The ARP-filter handles the subscriber-side ARP packets. ARP packets are not processed by subscriber-side SBRL.

  • The maximum rate is 255. Due to this, the configured rate of 256 from 16.8.X will not transfer properly. A new command must be entered to transfer the configuration.

Subscriber-MAC address SBRL identifies traffic streams by hashing the punt cause and the source MAC address. The hash value is used as the index for rate-limiting. Hash-collision detection is performed so that all traffic streams are processed separately.

Default settings for subscriber-side SBRL are listed in this topic. Using the 'no' configuration returns the rate to the default value.

Rate-limiting is performed using a 2-color token-bucket algorithm. The rate is specified in packets-per-4-seconds, in the range [1, 255]. This translates to a packets-per-second rate in the range [0.25, ~64]. The optional bucket-size is specified in packets, in the range [1, 255]. If not specified, then bucket-size is set equal to rate.

The "no-drop" keyword disables rate-limiting for the specified punt-cause.

There is an optional quarantine configuration. When a traffic stream enters quarantine, all punted packets in the stream are dropped for the configured period. A traffic stream enters quarantine when (burst-factor x rate) packets arrive at a rate faster than rate. An example would be that of a faulty cable modem that continuously sends DHCPv6 solicits.

  • DHCPv6 solicits from the faulty cable modem arrive at 100 packets/second, and are all punted.

  • Subscriber-side SBRL is configured with a rate-per-4-sec of 8 (i.e. 2 packets-per-sec), quarantine time of 10 minutes, and burst-factor of 500 packets.

The traffic stream rate is higher than the configured rate. Therefore, when approximately 1000 (2 x 500) packets have arrived, the traffic stream enters quarantine. The quarantine happens after about 10 seconds (1000 packets at 100 packets per second), and all punted packets from the stream are dropped for 10 minutes. After 10 minutes, the quarantine is deactivated. The quarantine calculations restart immediately, so if the traffic stream remains continuous, quarantine is reactivated after the next 10 seconds.

  1. enable 

    Router> enable

    Enables privileged EXEC mode. Enter your password, if prompted.

  2. configure terminal 

    Router# configure terminal

    Enters global configuration mode.

  3. platform punt-sbrl subscriber punt-cause punt-causerate-per-4-sec rate[ bucket-size bucket-size] [ quarantine-time time burst-factor burst-factor]

    Configures subscriber-MAC address SBRL.

    • punt-cause punt-cause - Specifies the punt cause.

    • rate-per-4-sec rate - Specifies the rate in packets per 4-seconds. The range is from 1 to 255.

    • bucket-size bucket-size – Specifies the bucket-size in packets. The range is from 1 to 255. If bucket-size is not entered, the bucket-size is set equal to the rate.

    • quarantine-time time – Specifies the quarantine time, in minutes. The range is from 1 to 60.

    • burst-factor burst-factor – Specifies the burst-factor, in number of packets. The range is from 50 to 1000.

Configuring Source-Based Rate Limit Ping-Bypass

Follow the steps below to configure source-based rate limit ping-bypass.

Procedure

  Command or Action Purpose
Step 1

enable

Example:

Router> enable

Enables privileged EXEC mode.

  • Enter your password, if prompted.

Step 2

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3

platform punt-sbrl ping-bypass

Example:

Router(config)# platform punt-sbrl ping-bypass

Configures source-based rate limit ping-bypass.

Configuring Punt Policing

The punt policer aggregates all packets (both subscriber-side and WAN-side) with the specified punt cause, and rate-limits them according to the configured parameters.

Procedure

  Command or Action Purpose
Step 1

enable

Example:

Router> enable

Enables privileged EXEC mode.

  • Enter your password, if prompted.

Step 2

configure terminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3

platform punt-policer { cable-snmp | punt-cause } punt-rate [ high]

Example:

Router(config)# platform punt-policer 1 10

Configures punt policing.

  • punt-cause—Specifies the punt cause value.

  • cable-snmp—This is the punt-cause assigned to SNMP packets destined to the CMTS.

  • punt-rate —Specifies the rate in packets/second. The range is from 10 to 300000.

  • high —(Optional) Specifies that the punt policing is performed only for high priority traffic.

Verifying the Source-Based Rate Limit Configuration

  • show cable dp sbrl config —Displays the SBRL configuration, including default settings. This is equivalent to show running-config all | include punt-sbrl .

    Following is a sample output of the command: 

    Router# show cable dp sbrl config
platform punt-sbrl wan punt-cause for-us-data rate-per-1-sec 8
platform punt-sbrl wan punt-cause glean-adj rate-per-1-sec 4 quarantine-time 10 burst-factor 1000
platform punt-sbrl subscriber punt-cause for-us-data rate-per-4-sec 32 bucket-size 32
platform punt-sbrl subscriber punt-cause for-us-ctrl rate-per-4-sec 8 bucket-size 8
platform punt-sbrl subscriber punt-cause cable-l3-mobility rate-per-4-sec 16 bucket-size 16
platform punt-sbrl subscriber punt-cause sv-match-unknown rate-per-4-sec 4 bucket-size 4
platform punt-sbrl subscriber punt-cause cable-pre-reg rate-per-4-sec 8 bucket-size 8
platform punt-sbrl subscriber punt-cause cbl-dhcpv6-solicit rate-per-4-sec 8 bucket-size 8
platform punt-sbrl subscriber punt-cause cbl-dhcpv6-req rate-per-4-sec 8 bucket-size 8
platform punt-sbrl subscriber punt-cause cbl-dhcpv6-sub rate-per-4-sec 8 bucket-size 8
platform punt-sbrl subscriber punt-cause cbl-dhcpv4-sub rate-per-4-sec 8 bucket-size 8
platform punt-sbrl subscriber punt-cause cbl-dhcpv4-disc-req rate-per-4-sec 8 bucket-size 8

  • show access-lists —Displays the access list information for verifying CoPP configuration.

    Following is a sample output of the command: 

    Router# show access-lists 

Extended IP access list 120
    10 permit ip any any dscp af31
    20 permit ip any any dscp cs2
    30 permit ip any any dscp af21
    40 permit ip 68.86.0.0 0.1.255.255 any
IPv6 access list TRUSTEDV6
    permit ipv6 2001:558::/32 any sequence 10

  • show policy-map policy-map-name —Displays the information for the policy map.

    Following is a sample output of the command: 

    Router# show policy-map copp_policy

  Policy Map copp_policy
    Class sbrl_trusted
     police rate 1000 pps
       conform-action transmit 
       exceed-action transmit 
    Class class-default
      set qos-group 99

  • show policy-map control-plane —Displays the control plane policy map information.

    Following is a sample output of the command: 

    Router# show policy-map control-plane

 Control Plane 

  Service-policy input: copp_policy

    Class-map: sbrl_trusted (match-any)  
      0 packets, 0 bytes
      5 minute offered rate 0000 bps, drop rate 0000 bps
      Match: access-group 120
      Match: access-group name TRUSTEDV6
      police:
          rate 1000 pps, burst 244 packets
        conformed 0 packets, 0 bytes; actions:
          transmit 
        exceeded 0 packets, 0 bytes; actions:
          transmit 
        conformed 0 pps, exceeded 0 pps

    Class-map: class-default (match-any)  
      28 packets, 4364 bytes
      5 minute offered rate 0000 bps, drop rate 0000 bps
      Match: any 
      QoS Set
        qos-group 99
          Marker statistics: Disabled

  • show platform hardware qfp active infrastructure punt sbrl —Displays the SBRL statistics.

    Following is a sample output of the command: 

    Router# show platform hardware qfp active infrastructure punt sbrl

SBRL statistics

Subscriber MAC-addr
  drop-cnt   evict-cnt  quar  MAC-Address      ID  punt-cause                                
-------------------------------------------------------------------------------------------
     10000       10000     0  0010.88a3.0456  101  cable-l3-mobility
 
WAN-IPv4
 drop-cnt   evict-cnt  quar  VRF  cause  IP-address
------------------------------------------------------
    456788      456788     0    0    050  1.2.0.66
 
WAN-IPv6
 drop-cnt   evict-cnt  quar  VRF  cause  IP-address
----------------------------------------------------------------------------
    129334      129334     1    0    011  3046:1829:fefb::ddd1
       965         965     0    0    011  2001:420:2c7f:fc01::3
 
. . .

    Note

    The value of quar is either 0 or 1. The value 1 indicates that quarantine is activated. The quar value is updated only when a packet from the source is dropped. If a source enters quarantine, and then stops sending packets, the quar value remains 1. However, the drop-cnt does not increment.


    Note

    The SBRL statistics algorithm stores the data for the worst offenders. Sources that drop only a few packets are displayed in the table initially, but may be overwritten if the drop-cnt does not increase continuously. The evict-cnt increases in tandem with drop-cnt, but begins to decrease when a source is no longer being actively rate-limited. When the evict-cnt drops below 10, the record may be overwritten.

  • show platform hardware qfp active infrastructure punt statistics type global-drop —Displays the global punt policer statistics.

    Following is a sample output of the command: 

    Router# show platform hardware qfp active infrastructure punt statistics type global-drop

Global Drop Statistics

  Number of global drop counters = 22

  Counter ID  Drop Counter Name                         Packets
  ---------------------------------------------------------------------
  000         INVALID_COUNTER_SELECTED                  0
  001         INIT_PUNT_INVALID_PUNT_MODE               0
  002         INIT_PUNT_INVALID_PUNT_CAUSE              0
  003         INIT_PUNT_INVALID_INJECT_CAUSE            0
  004         INIT_PUNT_MISSING_FEATURE_HDR_CALLBACK    0
  005         INIT_PUNT_EXT_PATH_VECTOR_REQUIRED        0
  006         INIT_PUNT_EXT_PATH_VECTOR_NOT_SUPPORTED   0
  007         INIT_INJ_INVALID_INJECT_CAUSE             0
  008         INIT_INJ_MISSING_FEATURE_HDR_CALLBACK     0
  009         PUNT_INVALID_PUNT_CAUSE                   0
  010         PUNT_INVALID_COMMON_HDR_VERSION           0
  011         PUNT_INVALID_PLATFORM_HDR_VERSION         0
  012         PUNT_PATH_NOT_INITIALIZED                 0
  013         PUNT_GPM_ALLOC_FAILURE                    0
  014         PUNT_TRANSITION_FAILURE                   0
  015         PUNT_DELAYED_PUNT_PKT_SB_NOT_IN_USE       0
  016         PUNT_CAUSE_GLOBAL_POLICER                 0
  017         INJ_INVALID_INJECT_CAUSE                  0
  018         INJ_INVALID_COMMON_HDR_VERSION            0
  019         INJ_INVALID_PLATFORM_HDR_VERSION          0
  020         INJ_INVALID_PAL_HDR_FORMAT                0
  021         PUNT_GPM_TX_LEN_EXCEED                    0

  • show platform hardware qfp active infrastructure punt summary [ threshold threshold-value] —Displays the punt path rate-limiting summary.

    Following is a sample output of the command: 

    Router# show platform hardware qfp active infrastructure punt summary

Punt Path Rate-Limiting summary statistics

Subscriber-side
ID   punt cause           CPP punt        CoPP  ARPfilt/SBRL   per-cause      global
------------------------------------------------------------------------------------
017  IPv6 Bad hop limit         22           0             0           0           0
050  IPv6 packet                13           0             0           0           0
080  CM not online             335           0             0           0           0
 
WAN-side
ID   punt cause           CPP punt        CoPP        SBRL   per-cause      global
------------------------------------------------------------------------------------
017 IPv6 Bad hop limit         471           0           0           0           0
018 IPV6 Hop-by-hop Options  29901           0           0        1430           0
024 Glean adjacency            111           0           0           0           0
025 Mcast PIM signaling         19           0           0           0           0
050 IPv6 packet                 11           0           0           0           0

  • show platform software punt-policer —Displays the punt policer configuration and statistics.

    Following is a sample output of the command: 

    Router# show platform software punt-policer

Per Punt-Cause Policer Configuration and Packet Counters

Punt                               Configured (pps) Conform Packets   Dropped Packets
Cause Description                  Normal   High    Normal     High   Normal     High
-------------------------------------------------------------------------------------
  2   IPv4 Options                 4000     3000    0          0      0          0
  3   Layer2 control and legacy    40000    10000   16038      0      0          0
  4   PPP Control                  2000     1000    0          0      0          0
  5   CLNS IS-IS Control           2000     1000    0          0      0          0
  6   HDLC keepalives              2000     1000    0          0      0          0
  7   ARP request or response      2000     1000    0          49165  0          0
  8   Reverse ARP request or re... 2000     1000    0          0      0          0
  9   Frame-relay LMI Control      2000     1000    0          0      0          0
 10   Incomplete adjacency         2000     1000    0          0      0          0
 11   For-us data                  40000    5000    279977     0      0          0
 12   Mcast Directly Connected ... 2000     1000    0          0      0          0
 . . .

  • show platform hardware qfp active infrastructure punt policer summary —Displays the punt policer summary.

    Following is a sample output of the command: 

    Router# show platform hardware qfp active infrastructure punt policer summary

QFP Punt Policer Config Summary


Policer  Rate     PeakRate   ConformBurst  ExceedBurst   Scaling
Handle   (pps)    (pps)      (pps)         (pps)         Factor
---------------------------------------------------------------------
001      300000   0          2288          2288          0
002      4000     0          4000          0             0
003      3000     0          3000          0             0
004      40000    0          40000         0             0
005      10000    0          10000         0             0
006      2000     0          2000          0             0
007      1000     0          1000          0             0
008      2000     0          2000          0             0
009      1000     0          1000          0             0
010      2000     0          2000          0             0
011      1000     0          1000          0             0
012      2000     0          2000          0             0
013      1000     0          1000          0             0
014      2000     0          2000          0             0
 . . .

Configuration Example for Source-Based Rate Limit

Example: WAN-Side SBRL Configuration 

access-list 120 permit ip any any dscp af31
access-list 120 permit ip any any dscp cs2
access-list 120 permit ip any any dscp af21 
access-list 120 permit ip 192.168.1.10 0.1.255.255 any

ipv6 access-list TRUSTEDV6
  permit ipv6 any any dscp af31
  permit ipv6 any any dscp cs2
  permit ipv6 any any dscp af21 
  permit ipv6 2001:558::/32 any 


class-map match-all sbrl_trusted_v4
  match access-group 120
 
class-map match-all sbrl_trusted_v6
  match access-group name TRUSTEDV6


policy-map copp_policy
  ! IPv4 trusted:
  !   Specified rate is irrelevant.
  !   No special action; these packets bypass WAN-side SBRL.
  class sbrl_trusted_v4
    police rate 1000 pps conform transmit exceed transmit
  ! IPv6 trusted:
  !   Specified rate is irrelevant.
  !   No special action; these packets bypass WAN-side SBRL.
  class sbrl_trusted_v6
    police rate 1000 pps conform transmit exceed transmit

  ! add other classes here, if necessary

  ! Special action to activate WAN-side SBRL for this class.
  class class-default
    set qos-group 99


control-plane
  service-policy input copp_policy

 
platform punt-sbrl wan punt-cause for-us-data rate-per-1-sec 4
platform punt-sbrl wan punt-cause glean-adj rate-per-1-sec 4 quarantine-time 10 burst-factor 1000

Example: Subscriber-Side SBRL Configuration 


platform punt-sbrl subscriber punt-cause cbl-dhcpv6-solicit rate-per-4-sec 2 bucket-size 8
platform punt-sbrl subscriber punt-cause sv-match-unknown rate-per-4-sec 4 bucket-size 10 quarantine-time 5 burst-factor 500

Default SBRL Configuration

Because of the dependency on CoPP, WAN-side SBRL is disabled by default. There is no default WAN-side SBRL configuration.

Subscriber-side SBRL has the following default settings:


platform punt-sbrl subscriber punt-cause for-us-data rate-per-4-sec 32 bucket-size 32
platform punt-sbrl subscriber punt-cause for-us-ctrl rate-per-4-sec 8 bucket-size 8
platform punt-sbrl subscriber punt-cause cable-l3-mobility rate-per-4-sec 16 bucket-size 16
platform punt-sbrl subscriber punt-cause sv-match-unknown rate-per-4-sec 4 bucket-size 4
platform punt-sbrl subscriber punt-cause cable-pre-reg rate-per-4-sec 8 bucket-size 8
platform punt-sbrl subscriber punt-cause cbl-dhcpv6-solicit rate-per-4-sec 8 bucket-size 8
platform punt-sbrl subscriber punt-cause cbl-dhcpv6-req rate-per-4-sec 8 bucket-size 8
platform punt-sbrl subscriber punt-cause cbl-dhcpv6-sub rate-per-4-sec 8 bucket-size 8
platform punt-sbrl subscriber punt-cause cbl-dhcpv4-disc-req rate-per-4-sec 8 bucket-size 8
platform punt-sbrl subscriber punt-cause cbl-dhcpv4-sub rate-per-4-sec 8 bucket-size 8

Conversion of SBRL Subscriber-side Configuration from 16.8.x to 16.9.x

In 16.9.x, several new punt-causes were added for DHCP packets on the subscriber-side. This means that the recommended configuration for 16.8.x does not match up with the default configuration in 16.9.x.

In 16.8.x, the cable-dhcp punt-cause is used by both subscriber-side and WAN-side DHCP punts. In 16.9.x, new punt-causes were added on the subscriber-side for DHCP packets, with the result that the cable-dhcp punt-cause is used ONLY for WAN-side DHCP punts. This means that configuring a rate for cable-dhcp on the subscriber-side is meaningless. The chart below shows the DHCP-related punt-causes for 16.8.x and 16.9.x. In 16.9.x, all the subscriber-side DHCP punt-causes have default SBRL settings.

Table 2. 16.8.x

punt-cause

Origin

Description

cbl-dhcpv6-solicit

sub

DHCPv6 solicit

cbl-dhcpv6-req

sub

DHCPv6 request

cable-dhcp

sub/WAN

all other DHCP packets
Table 3. 16.9.x

punt-cause

Origin

Description

cbl-dhcpv6-solicit

sub

DHCPv6 solicit

cbl-dhcpv6-req

sub

DHCPv6 request

cbl-dhcpv6-sub

sub

all other (sub-side) DHCPv6 packets

cbl-dhcpv4-disc-req

sub

DHCPv4 discover & request

cbl-dhcpv4-sub

sub

all other (sub-side) DHCPv4 packets

cable-dhcp

WAN

all (WAN-side) DHCP packets

Conversion of Divert Rate Limit Configuration on the Cisco uBR10012 Router to SBRL Configuration on the Cisco cBR Series Routers

Divert Rate Limit Configuration on the Cisco uBR10012 Router

The following is a sample Divert Rate Limit (DRL) configuration on the Cisco uBR10012 router: 


service divert-rate-limit ip fib_rp_glean rate 4 limit 4      
service divert-rate-limit ip fib_rp_dest rate 4 limit 4       
service divert-rate-limit ip fib_rp_punt rate 4 limit 4       
service divert-rate-limit ipv6 ipv6_rp_dest rate 4 limit 4    
service divert-rate-limit ipv6 ipv6_rp_punt rate 4 limit 4    
service divert-rate-limit ipv6 ipv6_rp_glean rate 4 limit 4   
service divert-rate-limit ipv6 icmpv6 rate 4 limit 4          
 
service divert-rate-limit trusted-site 0.0.0.0 0.0.0.0 tos 0x68 mask 0xFF
service divert-rate-limit trusted-site 0.0.0.0 0.0.0.0 tos 0x40 mask 0xFF
service divert-rate-limit trusted-site 68.86.0.0 255.254.0.0 tos 0x0 mask 0x0
service divert-rate-limit trusted-site 0.0.0.0 0.0.0.0 tos 0x48 mask 0xFF
service divert-rate-limit trusted-site-ipv6 ::/0 traffic-class 0x40 mask 0xFF
service divert-rate-limit trusted-site-ipv6 ::/0 traffic-class 0x48 mask 0xFF
service divert-rate-limit trusted-site-ipv6 ::/0 traffic-class 0x68 mask 0xFF
service divert-rate-limit trusted-site-ipv6 2001:558::/32 traffic-class 0x0 mask 0x0
 
interface Cablex/y/z
   cable divert-rate-limit rate 4 limit 30

In Cisco IOS Release 12.2(33)SCH2, the divert-rate-limit max-rate wan command was introduced on the Cisco uBR10012 router. This configuration limits the aggregate rate of diverted packets on the WAN-side, on a per-divert-code basis. The following is the recommended best-practice configuration for the divert-rate-limit max-rate wan command: 

service divert-rate-limit max-rate wan fib_rp_glean rate 5000
service divert-rate-limit max-rate wan fib_rp_punt rate 5000
service divert-rate-limit max-rate wan fib_rp_dest rate 40000
 
service divert-rate-limit max-rate wan ipv6_fib_glean rate 5000
service divert-rate-limit max-rate wan ipv6_fib_punt rate 5000
service divert-rate-limit max-rate wan ipv6_fib_dest rate 40000

SBRL Configuration on the Cisco cBR Series Routers

The DRL functionality is called as Source-Based Rate Limit (SBRL) on the Cisco cBR Series Routers. The punt-path has three layers of protection:

CoPP

CoPP is used to specify the trusted sites and activate WAN-side SBRL. However, since CoPP applies to all punted packets, you must ensure that cable-side punts do not match the trusted sites.

The following is a sample CoPP configuration, which is equivalent to the configuration on the Cisco uBR10012 router: 

access-list 120 permit ip any any dscp af31
access-list 120 permit ip any any dscp cs2
access-list 120 permit ip any any dscp af21 
access-list 120 permit ip 68.86.0.0 0.1.255.255 any
 
ipv6 access-list TRUSTEDV6
   permit ipv6 any any dscp af31
   permit ipv6 any any dscp cs2
   permit ipv6 any any dscp af21 
   permit ipv6 2001:558::/32 any 
 
class-map match-all sbrl_trusted_v4
   match access-group 120
 
class-map match-all sbrl_trusted_v6
   match access-group name TRUSTEDV6
  
policy-map copp_policy
   class sbrl_trusted_v4
     police rate 1000 pps conform transmit exceed transmit
   class sbrl_trusted_v6
     police rate 1000 pps conform transmit exceed transmit
   class class-default
     set qos-group 99
  
control-plane
   service-policy input copp_policy

Note

  • The set qos-group 99 command activates SBRL for the specified class.

  • The police rate for sbrl_trusted_vx is irrelevant, as both actions are set to transmit .

  • You can add other trusted sites, as necessary.

SBRL

The following subscriber-side SBRL configuration is recommended. This configuration covers the expected subscriber-side punt-causes. 

platform punt-sbrl subscriber punt-cause for-us-data rate-per-4-sec 32
platform punt-sbrl subscriber punt-cause for-us-ctrl rate-per-4-sec 8
platform punt-sbrl subscriber punt-cause sv-match-unknown rate-per-4-sec 4
platform punt-sbrl subscriber punt-cause cable-pre-reg rate-per-4-sec 8
platform punt-sbrl subscriber punt-cause cable-dhcp rate-per-4-sec 8
platform punt-sbrl subscriber punt-cause cbl-dhcpv6-solicit rate-per-4-sec 8
platform punt-sbrl subscriber punt-cause cbl-dhcpv6-req rate-per-4-sec 8

The recommended subscriber-side SBRL configuration is the default configuration. All expected subscriber-side punt-causes have default settings.

For WAN-side SBRL, the Cisco cBR Series routers do not have separate IPv4 and IPv6 configurations as the punt causes are shared between IPv4 and IPv6. The limit cannot be configured as the hardware policer is used. Therefore, we recommend that you configure a higher rate initially. In the following sample configuration, glean-adj and for-us-data correspond to x_rp_glean and x_rp_dest, respectively on the Cisco uBR 10012 router. 


platform punt-sbrl wan punt-cause for-us-data rate 8
platform punt-sbrl wan punt-cause glean-adj rate 8

Note

  • The fib-punt punt cause is used in the Cisco uBR10012 router for packets destined to the management Ethernet. This punt cause is not used on the Cisco cBR Series routers.

  • The Cisco cBR Series routers do not have an equivalent punt cause for ICMPV6. In the Cisco uBR10012 routers, ICMPv6 packets must be processed by the Route Processor to generate the checksum. In the Cisco cBR Series routers, ICMPv6 is processed in the control-plane. However, ICMPv6 punts can be identified and rate-limited (in aggregate) using CoPP.

Punt Policer

The punt policer operates on all punt causes and is fully configurable. The punt policer is not divided into WAN-side and subscriber-side. All packets with a given punt cause are aggregated and rate-limited as configured.

Following are the default settings (best-practice configuration) for the punt policer on the Cisco cBR Series routers: 

punt-cause                      LO     HI
 
CPP_PUNT_CAUSE_GLEAN_ADJ        2000   5000
CPP_PUNT_CAUSE_FOR_US           40000  5000

Note

  • The equivalent punt cause for fib-glean (on the Cisco uBR10012 router) is GLEAN_ADJ/HI on the Cisco cBR Series routers.

  • The equivalent punt cause for fib-dest (on the Cisco uBR10012 router) is FOR_US/LO on the Cisco cBR Series routers.

Additional References

Related Documents

Related Topic Document Title
Cisco IOS commands Cisco IOS Master Commands List, All Releases

Technical Assistance

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Feature Information for Source-Based Rate Limit

Use Cisco Feature Navigator to find information about the 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 the https://cfnng.cisco.com/ link. An account on the Cisco.com page is not required.


Note

The following table lists the software release in which a given feature is introduced. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Table 4. Feature Information for Source-Based Rate Limit

Feature Name

Releases

Feature Information

Source-based rate limit

Cisco IOS XE Everest 16.6.1

This feature was integrated into Cisco IOS XE Everest 16.6.1 on theCisco cBR Series Converged Broadband Routers.

Source-based rate limit

Cisco IOS XE Gibraltar 16.12.1z1

A new punt cause cable-snmp was added to rate-limit the SNMP packets destined to the CMTS.