NetFlow Configuration Guide, Cisco IOS Release 15M&T
Configuring NetFlow Multicast Accounting
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Configuring NetFlow Multicast Accounting

Contents

Configuring NetFlow Multicast Accounting

This document contains information about and instructions for configuring NetFlow multicast accounting. NetFlow multicast accounting allows you to capture multicast-specific data (both packets and bytes) for multicast flows.

NetFlow is a Cisco IOS application that provides statistics on packets flowing through the router. It is emerging as a primary network accounting and security technology.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

Prerequisites for Configuring NetFlow Multicast Accounting

Before you can configure NetFlow multicast accounting, you must:

  • Configure the router for IP routing

  • Configure Multicast fast switching or multicast distributed fast switching (MDFS); multicast Cisco Express Forwarding (CEF) switching is not supported.

  • Configure Multicast routing.

  • Configure NetFlow v9 (Version 9) data export (otherwise, multicast data is visible in the cache but is not exported).

Restrictions for Configuring NetFlow Multicast Accounting

Memory Impact

If traffic is heavy, the additional flows might fill the global flow hash table. If you must increase the size of the global flow hash table, you must also add memory to the router.

NetFlow has a maximum cache size of 65,536 flow record entries of 64 bytes each. To deduce the packet-replication factor, multicast accounting adds 16 bytes (for a total of 80 bytes) to each multicast flow record.

Performance Impact

Ingress multicast accounting does not greatly affect performance. Because of the additional accounting-related computation that occurs in the traffic-forwarding path of the router, egress NetFlow multicast accounting might degrade network performance slightly, but it does not limit the functionality of the router.

Multicast Addresses

NetFlow data cannot be exported to multicast addresses.

Information About Configuring NetFlow Multicast Accounting

NetFlow Multicast Benefits

NetFlow multicast allows you to capture multicast-specific data (both packets and bytes) for multicast flows. For example, you can capture the packet-replication factor for a specific flow as well as for each outgoing stream. NetFlow multicast provides complete end-to-end usage information about network traffic for a complete multicast traffic billing solution.

You can use NetFlow multicast accounting to identify and count multicast packets on the ingress side or the egress side (or both sides) of a router. Multicast ingress accounting provides information about the source and how many times the traffic was replicated. Multicast egress accounting monitors the destination of the traffic flow.

NetFlow multicast lets you enable NetFlow statistics to account for all packets that fail the reverse path forwarding (RPF) check and that are dropped in the core of the service provider network. Accounting for RPF-failed packets provides more accurate traffic statistics and patterns.

Multicast Ingress and Multicast Egress Accounting

NetFlow multicast lets you select either multicast ingress accounting, in which a replication factor (equal to the number of output interfaces) indicates the load, or multicast egress accounting, in which all outgoing multicast streams are counted as separate streams, or both multicast ingress and multicast egress accounting.

NetFlow multicast lets you collect information about how much data is leaving the interfaces of the router (egress and multicast ingress accounting) or how much multicast data is received (multicast ingress accounting).

On the ingress side, multicast packets are counted as with unicast packets, but with two additional fields (for number of replicated packets and byte count). With multicast ingress accounting, the destination interface field is set to null, and the IP next hop field is set to 0 for multicast flows.

NetFlow Multicast Flow Records

Multicast ingress accounting creates one flow record that indicates how many times each packet is replicated. Multicast egress accounting creates a unique flow record for each outgoing interface.

How to Configure NetFlow Multicast Accounting

Configuring NetFlow Multicast Accounting in Releases 12.4(12)

Perform the steps in this required task to configure NetFlow multicast accounting.

Before You Begin

You must have already configured IP multicast on the networking devices in your network. See the Cisco IOS IP Multicast Configuration Guide , for more information on configuring IP multicast.

SUMMARY STEPS

    1.    enable

    2.    configure terminal

    3.    ip multicast-routing [vrf vrf-name] [distributed]

    4.    ip multicast netflow rpf-failure

    5.    ip multicast netflow output-counters

    6.    interface type number

    7.    ip flow ingress

    8.    end


DETAILED STEPS
     Command or ActionPurpose
    Step 1 enable


    Example:
    Router> enable
     

    Enters privileged EXEC mode.

    • Enter your password if prompted.

     
    Step 2 configure terminal


    Example:
    Router# configure terminal
     

    Enters global configuration mode.

     
    Step 3 ip multicast-routing [vrf vrf-name] [distributed]


    Example:
    Router(config)# ip multicast-routing
     

    Enables IP multicast routing.

    • The vrf keyword supports the multicast Virtual Private Network (VPN) routing/forwarding instance (VRF).

    • The vrf-name argument is the name assigned to the VRF.

    • The distributed keyword enables Multicast Distributed Switching (MDS).

     
    Step 4 ip multicast netflow rpf-failure


    Example:
    Router(config)# ip multicast netflow rpf-failure
     

    Enables accounting for multicast data that fails the RPF check.

     
    Step 5 ip multicast netflow output-counters


    Example:
    Router(config)# ip multicast netflow output-counters
     

    Enables accounting for the number of bytes and packets forwarded.

     
    Step 6 interface type number


    Example:
    Router(config)# interface fastethernet 0/0
     

    Specifies the interface and enters interface configuration mode.

     
    Step 7 ip flow ingress


    Example:
    Router(config-if)# ip flow ingress
     

    Enables NetFlow ingress accounting.

     
    Step 8 end


    Example:
    Router(config-if)# end
     

    Exits the current configuration mode and returns to privileged EXEC mode.

     

    Troubleshooting Tips

    If there are no multicast flow records in the NetFlow cache, check the multicast switching counters for the existence of process-switched packets (NetFlow exports only fast-switched or MDFS-switched packets). If process-switched packets are present, check the MDFS routing table to help determine potential problems.

    Configuring NetFlow Multicast Accounting in Cisco IOS Releases Prior to 12.4(12)

    Configuring NetFlow Multicast Egress Accounting

    Perform the steps in this required task to configure NetFlow multicast egress accounting.

    Before You Begin

    You must have already configured IP multicast on the networking devices in your network. See the Cisco IOS IP Multicast Configuration Guide, for more information on configuring IP multicast.

    SUMMARY STEPS

      1.    enable

      2.    configure terminal

      3.    ip multicast-routing [vrf vrf-name] [distributed]

      4.    ip multicast netflow rpf-failure

      5.    interface type number

      6.    ip multicast netflow egress

      7.    end


    DETAILED STEPS
       Command or ActionPurpose
      Step 1 enable


      Example:
      Router> enable
       

      Enters privileged EXEC mode.

      • Enter your password if prompted.

       
      Step 2 configure terminal


      Example:
      Router# configure terminal
       

      Enters global configuration mode.

       
      Step 3 ip multicast-routing [vrf vrf-name] [distributed]


      Example:
      Router(config)# ip multicast-routing


      Example:
      
      
              
       

      Enables IP multicast routing.

      • The vrf keyword supports the multicast Virtual Private Network (VPN) routing/forwarding instance (VRF).

      • The vrf-name argument is the name assigned to the VRF.

      • The distributed keyword enables Multicast Distributed Switching (MDS).

       
      Step 4 ip multicast netflow rpf-failure


      Example:
      Router(config)# ip multicast netflow rpf-failure
       

      Enables accounting for multicast data that fails the RPF check.

       
      Step 5 interface type number


      Example:
      Router(config)# interface fastethernet 0/0
       

      Specifies the interface and enters interface configuration mode.

       
      Step 6 ip multicast netflow egress


      Example:
      Router(config-if)# ip multicast netflow egress
       

      Enables NetFlow multicast egress accounting.

       
      Step 7 end


      Example:
      Router(config-if)# end
       

      Exits the current configuration mode and returns to privileged EXEC mode.

       
      Troubleshooting Tips

      If there are no multicast flow records in the NetFlow cache, check the multicast switching counters for the existence of process-switched packets (NetFlow exports only fast-switched or MDFS-switched packets). If process-switched packets are present, check the MDFS routing table to help determine potential problems.

      Configuring NetFlow Multicast Ingress Accounting

      Perform the steps in this required task to configure NetFlow multicast ingress accounting.

      Multicast ingress NetFlow accounting is enabled by default.

      Before You Begin

      You must have already configured IP multicast on the networking devices in your network. See the Cisco IOS IP Multicast Configuration Guide, for more information on configuring IP multicast.

      SUMMARY STEPS

        1.    enable

        2.    configure terminal

        3.    ip multicast-routing [vrf vrf-name] [distributed]

        4.    ip multicast netflow rpf-failure

        5.    interface type number

        6.    ip multicast netflow ingress

        7.    end


      DETAILED STEPS
         Command or ActionPurpose
        Step 1 enable


        Example:
        Router> enable
         

        Enters privileged EXEC mode.

        • Enter your password if prompted.

         
        Step 2 configure terminal


        Example:
        Router# configure terminal
         

        Enters global configuration mode.

         
        Step 3 ip multicast-routing [vrf vrf-name] [distributed]


        Example:
        Router(config)# ip multicast-routing


        Example:
        
        
                
         

        Enables IP multicast routing.

        • The vrf keyword supports the multicast VRF.

        • The vrf-name argument is the name assigned to the VRF.

        • The distributed keyword enables Multicast Distributed Switching (MDS).

         
        Step 4 ip multicast netflow rpf-failure


        Example:
        Router(config)# ip multicast netflow rpf-failure
         

        Enables accounting for multicast data that fails the RPF check.

         
        Step 5 interface type number


        Example:
        Router(config)# interface fastethernet 0/0
         

        Specifies the interface and enters interface configuration mode.

         
        Step 6 ip multicast netflow ingress


        Example:
        Router(config-if)# ip multicast netflow ingress
         

        Enables NetFlow multicast ingress accounting.

         
        Step 7 end


        Example:
        Router(config-if)# end
         

        Exits the current configuration mode and returns to privileged EXEC mode.

         
        Troubleshooting Tips

        If there are no multicast flow records in the NetFlow cache, check the multicast switching counters for the existence of process-switched packets (NetFlow exports only fast-switched or MDFS-switched packets). If process-switched packets are present, check the MDFS routing table to help determine potential problems.

        Verifying the NetFlow Multicast Accounting Configuration

        Perform the steps in this optional task to verify the NetFlow multicast accounting configuration.

        SUMMARY STEPS

          1.    enable

          2.    show ip cache verbose flow


        DETAILED STEPS
          Step 1   enable

          Use this command to enable privileged EXEC mode. Enter your password if required. For example:



          Example:
          Router> enable
          Router#
          
          Step 2   show ip cache verbose flow

          Use this command to verify that NetFlow multicast accounting is configured. Look for the two additional fields related to multicast data, that is, the number of IP multicast output packet and byte counts. For example:



          Example:
          Router# show ip cache verbose flow
          IP packet size distribution (5149 total packets):
             1-32   64   96  128  160  192  224  256  288  320  352  384  416  448  480
             .997 .002 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000
              512  544  576 1024 1536 2048 2560 3072 3584 4096 4608
             .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000
          IP Flow Switching Cache, 278544 bytes
            2 active, 4094 inactive, 14 added
            468 ager polls, 0 flow alloc failures
            Active flows timeout in 30 minutes
            Inactive flows timeout in 15 seconds
          IP Sub Flow Cache, 25800 bytes
            1 active, 1023 inactive, 1 added, 1 added to flow
            0 alloc failures, 0 force free
            1 chunk, 1 chunk added
            last clearing of statistics never
          Protocol         Total    Flows   Packets Bytes  Packets Active(Sec) Idle(Sec)
          --------         Flows     /Sec     /Flow  /Pkt     /Sec     /Flow     /Flow
          UDP-other           12      0.0         1    52      0.0       0.1      15.6
          Total:              12      0.0         1    52      0.0       0.1      15.6
          SrcIf          SrcIPaddress    DstIf          DstIPaddress    Pr TOS Flgs  Pkts
          Port Msk AS                    Port Msk AS    NextHop              B/Pk  Active
          IPM: OPkts    OBytes   
          Et0/0          10.1.1.1        Null           224.192.16.1    01 55  10    5164 
          0000 /0  0                     0000 /0  0     0.0.0.0                20   262.8
          IPM:    15K    309K 
          Et0/0          10.1.1.1        Null           255.255.255.255 11 C0  10       1 
          0208 /0  0                     0208 /0  0     0.0.0.0                52     0.0
          Router#
          

          The Opkts column displays the number of IP multicast (IPM) output packets, the OBytes column displays the number of IPM output bytes, and the DstIPaddress column displays the destination IP address for the IPM output packets.


          Configuration Examples for NetFlow Multicast Accounting

          Configuring NetFlow Multicast Accounting in Original Releases

          The following example shows how to configure multicast NetFlow accounting:

          configure terminal
           ip multicast-routing
           ip multicast netflow rpf-failure
           ip multicast netflow output-counters
          !
          interface ethernet 0/0
           ip flow ingress
           end

          Configuring NetFlow MC Accounting in Releases Prior to 12.2(33)SRB

          Configuring NetFlow Multicast Egress Accounting Example

          The following example shows how to configure multicast egress NetFlow accounting on the egress Ethernet 0/0 interface:

          configure terminal
           ip multicast-routing
           ip multicast netflow rpf-failure
          !
          interface ethernet 0/0
           ip multicast netflow egress
           end
          

          Configuring NetFlow Multicast Ingress Accounting Example

          The following example shows how to configure multicast ingress NetFlow accounting on the ingress Ethernet 1/0 interface:

          configure terminal
           ip multicast-routing
           ip multicast netflow rpf-failure
          !
          interface ethernet 1/0
           ip multicast netflow ingress
           end
          

          Additional References

          Related Documents

          Related Topic

          Document Title

          Overview of Cisco IOS NetFlow

          Cisco IOS NetFlow Overview

          The minimum information about and tasks required for configuring NetFlow and NetFlow Data Export

          Getting Started with Configuring NetFlow and NetFlow Data Export

          Tasks for configuring NetFlow to capture and export network traffic data

          Configuring NetFlow and NetFlow Data Export

          Tasks for configuring Configuring MPLS Aware NetFlow

          Configuring MPLS Aware NetFlow

          Tasks for configuring MPLS egress NetFlow accounting

          Configuring MPLS Egress NetFlow Accounting and Analysis

          Tasks for configuring NetFlow input filters

          Using NetFlow Filtering or Sampling to Select the Network Traffic to Track

          Tasks for configuring Random Sampled NetFlow

          Using NetFlow Filtering or Sampling to Select the Network Traffic to Track

          Tasks for configuring NetFlow aggregation caches

          Configuring NetFlow Aggregation Caches

          Tasks for configuring NetFlow BGP next hop support

          Configuring NetFlow BGP Next Hop Support for Accounting and Analysis

          Tasks for detecting and analyzing network threats with NetFlow

          Detecting and Analyzing Network Threats With NetFlow

          Tasks for configuring NetFlow Reliable Export With SCTP

          NetFlow Reliable Export With SCTP

          Tasks for configuring NetFlow Layer 2 and Security Monitoring Exports

          NetFlow Layer 2 and Security Monitoring Exports

          Tasks for configuring the SNMP NetFlow MIB

          Configuring SNMP and using the NetFlow MIB to Monitor NetFlow Data

          Tasks for configuring the NetFlow MIB and Top Talkers feature

          Configuring NetFlow Top Talkers using Cisco IOS CLI Commands or SNMP Commands

          Information for installing, starting, and configuring the CNS NetFlow Collection Engine

          Cisco CNS NetFlow Collection Engine Documentation

          Standards

          Standards

          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

          No new or modified MIBS are supported by this feature, and support for existing MIBs has not been modified by this feature.

          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

          No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature.

          --

          Technical Assistance

          Description

          Link

          The Cisco Technical Support website contains thousands of 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.com/​techsupport

          Feature Information for Configuring NetFlow Multicast Accounting

          The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

          Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

          Table 1 Feature Information for Configuring NetFlow Multicast Accounting

          Feature Name

          Releases

          Feature Configuration Information

          NetFlow Multicast Support

          12.3(1), 12.2(18)S, 12.2(27)SBC, 12.2(33)SXF, 12.2(33)SRB

          The NetFlow Multicast Support feature lets you capture multicast-specific data (both packets and bytes) for multicast flows. For example, you can capture the packet-replication factor for a specific flow as well as for each outgoing stream. This feature provides complete end-to-end usage information about network traffic for a complete multicast traffic billing solution.

          The following commands were introduced by this feature: ip multicast netflow egress, ip multicast netflow ingress, and ip multicast netflow rpf-failure.

          NetFlow Multicast Support1

          12.4(11)T, 12.4(12), 12.(33)SRB, 12.2(33)SB, 12.2(33)SXH

          The ip multicast netflow [ingress | egress] interface configuration command was replaced by the ip multicast netflow output-counters global configuration command.

          1 This was a minor modification to the existing NetFlow Multicast Support feature. Minor feature modifications are not included in Feature Navigator.

          Glossary

          CEF --Cisco Express Forwarding. A Layer 3 IP switching technology that optimizes network performance and scalability for networks with large and dynamic traffic patterns.

          dCEF --distributed Cisco Express Forwarding. A type of CEF switching in which line cards (such as Versatile Interface Processor (VIP) line cards) maintain identical copies of the forwarding information base (FIB) and adjacency tables. The line cards perform the express forwarding between port adapters; this relieves the Route Switch Processor of involvement in the switching operation.

          egress traffic --Traffic leaving the network.

          fast switching --Cisco feature in which a route cache is used for expediting packet switching through a router.

          ingress traffic --Traffic entering the network.

          multicast data --Single packets copied by the network and sent to a specific subset of network addresses. These addresses are specified in the Destination Address field.

          NetFlow --A Cisco IOS application that provides statistics on packets flowing through the router. It is emerging as a primary network accounting and security technology.

          NetFlow Aggregation --A NetFlow feature that lets you summarize NetFlow export data on an IOS router before the data is exported to a NetFlow data collection system such as the NetFlow Collection Engine. This feature lowers bandwidth requirements for NetFlow export data and reduces platform requirements for NetFlow data collection devices.

          NetFlow Collection Engine (formerly called NetFlow FlowCollector)--A Cisco application that is used with NetFlow on Cisco routers and Catalyst series switches. The NetFlow Collection Engine collects packets from the router that is running NetFlow and decodes, aggregates, and stores them. You can generate reports on various aggregations that can be set up on the NetFlow Collection Engine.

          NetFlow v9 --NetFlow export format Version 9. A flexible and extensible means for carrying NetFlow records from a network node to a collector. NetFlow Version 9 has definable record types and is self-describing for easier NetFlow Collection Engine configuration.

          RPF --Reverse Path Forwarding. Multicasting technique in which a multicast datagram is forwarded out of all but the receiving interface if the receiving interface is the one used to forward unicast datagrams to the source of the multicast datagram.

          ToS byte --type of service byte. Second byte in the IP header that indicates the desired quality of service (QoS) for a particular datagram.