Cisco ASR 9000 Series Aggregation Services Router IP Addresses and Services Configuration Guide, Release 4.1
Implementing Cisco Express Forwarding
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Implementing Cisco Express Forwarding

Contents

Implementing Cisco Express Forwarding

Cisco Express Forwarding (CEF) is advanced, Layer 3 IP switching technology. CEF optimizes network performance and scalability for networks with large and dynamic traffic patterns, such as the Internet, on networks characterized by intensive web-based applications, or interactive sessions.

This module describes the tasks required to implement CEF on your Cisco ASR 9000 Series Aggregation Services Router.


Note


For complete descriptions of the CEF commands listed in this module, refer to the Cisco ASR 9000 Series Aggregation Services Router IP Addresses and Services Command Reference . To locate documentation for other commands that might appear in the course of executing a configuration task, search online in the master command index.


Feature History for Implementing CEF

Release

Modification

Release 3.7.2

This feature was introduced.

Prerequisites for Implementing Cisco Express Forwarding

The following prerequisites are required to implement Cisco Express Forwarding:

  • You must be in a user group associated with a task group that includes the proper task IDs. The command reference guides include the task IDs required for each command. If you suspect user group assignment is preventing you from using a command, contact your AAA administrator for assistance.

Information About Implementing Cisco Express Forwarding Software

To implement Cisco Express Forwarding features in this document you must understand the following concepts:

Key Features Supported in the Cisco Express Forwarding Implementation

The following features are supported for CEF on Cisco IOS XR software:

  • Border Gateway Protocol (BGP) policy accounting
  • Reverse path forwarding (RPF)
  • Virtual interface support
  • Multipath support
  • Route consistency
  • High availability features such as packaging, restartability, and Out of Resource (OOR) handling
  • OSPFv2 SPF prefix prioritization
  • BGP attributes download

Benefits of CEF

CEF offers the following benefits:

  • Improved performance—CEF is less CPU-intensive than fast-switching route caching. More CPU processing power can be dedicated to Layer 3 services such as quality of service (QoS) and encryption.
  • Scalability—CEF offers full switching capacity at each modular services card (MSC).
  • Resilience—CEF offers an unprecedented level of switching consistency and stability in large dynamic networks. In dynamic networks, fast-switched cache entries are frequently invalidated due to routing changes. These changes can cause traffic to be process switched using the routing table, rather than fast switched using the route cache. Because the Forwarding Information Base (FIB) lookup table contains all known routes that exist in the routing table, it eliminates route cache maintenance and the fast-switch or process-switch forwarding scenario. CEF can switch traffic more efficiently than typical demand caching schemes.

CEF Components

Cisco IOS XR softwareCEF always operates in CEF mode with two distinct components: a Forwarding Information Base (FIB) database and adjacency table—a protocol-independent adjacency information base (AIB).

CEF is a primary IP packet-forwarding database for Cisco IOS XR software. CEF is responsible for the following functions:

  • Software switching path
  • Maintaining forwarding table and adjacency tables (which are maintained by the AIB) for software and hardware forwarding engines

The following CEF forwarding tables are maintained in Cisco IOS XR software:

  • IPv4 CEF database
  • IPv6 CEF database
  • MPLS LFD database
  • Multicast Forwarding Table (MFD)

The protocol-dependent FIB process maintains the forwarding tables for IPv4 and IPv6 unicast in the Route Switch Processor (RSP ) and each MSC.

The FIB on each node processes Routing Information Base (RIB) updates, performing route resolution and maintaining FIB tables independently in the RSP and each MSC. FIB tables on each node can be slightly different. Adjacency FIB entries are maintained only on a local node, and adjacency entries linked to FIB entries could be different.

Border Gateway Protocol Policy Accounting

Border Gateway Protocol (BGP) policy accounting measures and classifies IP traffic that is sent to, or received from, different peers. Policy accounting is enabled on an individual input or output interface basis, and counters based on parameters such as community list, autonomous system number, or autonomous system path are assigned to identify the IP traffic.


Note


There are two types of route policies. The first type (regular BGP route policies) is used to filter the BGP routes advertised into or out from the BGP links. This type of route policy is applied to the specific BGP neighbor. The second type (specific route policy) is used to set up a traffic index for the BGP prefixes. This route policy is applied to the global BGP IPv4 address family to set up the traffic index when the BGP routes are inserted into the RIB table. BGP policy accounting uses the second type of route policy.


Using BGP policy accounting, you can account for traffic according to the route it traverses. Service providers can identify and account for all traffic by customer and bill accordingly. In Figure 1, BGP policy accounting can be implemented in Router A to measure packet and byte volumes in autonomous system buckets. Customers are billed appropriately for traffic that is routed from a domestic, international, or satellite source.


Note


BGP policy accounting measures and classifies IP traffic for BGP prefixes only.


Figure 1. Sample Topology for BGP Policy Accounting

Based on the specified routing policy, BGP policy accounting assigns each prefix a traffic index (bucket) associated with an interface. BGP prefixes are downloaded from the RIB to the FIB along with the traffic index.

There are a total of 63 (1 to 63) traffic indexes (bucket numbers) that can be assigned for BGP prefixes. Internally, there is an accounting table associated with the traffic indexes to be created for each input (ingress) and output (egress) interface. The traffic indexes allow you to account for the IP traffic, where the source IP address, the destination IP address, or both are BGP prefixes.


Note


Traffic index 0 contains the packet count using Interior Gateway Protocol (IGP) routes.


Reverse Path Forwarding (Strict and Loose)

Unicast IPv4 and IPv6 Reverse Path Forwarding (uRPF), both strict and loose modes, help mitigate problems caused by the introduction of malformed or spoofed IP source addresses into a network by discarding IP packets that lack a verifiable IP source address. Unicast RPF does this by doing a reverse lookup in the CEF table. Therefore, Unicast Reverse Path Forwarding is possible only if CEF is enabled on the router.


Note


Unicast RPF allows packets with 0.0.0.0 source addresses and 255.255.255.255 destination addresses to pass so that Bootstrap Protocol and Dynamic Host Configuration Protocol (DHCP) will function properly.


When strict uRPF is enabled, the source address of the packet is checked in the FIB. If the packet is received on the same interface that would be used to forward the traffic to the source of the packet, the packet passes the check and is further processed; otherwise, it is dropped. Strict uRPF should only be applied where there is natural or configured symmetry. Because internal interfaces are likely to have routing asymmetry, that is, multiple routes to the source of a packet, strict uRPF should not be implemented on interfaces that are internal to the network.


Note


The behavior of strict RPF varies slightly by platform, number of recursion levels, and number of paths in Equal-Cost Multipath (ECMP) scenarios. A platform may switch to loose RPF check for some or all prefixes, even though strict RPF is configured.


When loose uRPF is enabled, the source address of the packet is checked in the FIB. If it exists and matches a valid forwarding entry, the packet passes the check and is further processed; otherwise, it is dropped.

Strict mode uRPF requires maintenance of uRPF interfaces list for the prefixes. The list contains only strict mode uRPF configured interfaces pointed by the prefix path. uRPF interface list is shared among the prefixes wherever possible. Size of this list is 12 for ASR 9000 Ethernet Line Cards and 64 for integrated 20G SIP cards. Strict to loose mode uRPF fallback happens when the list goes beyond the maximum supported value.

Loose and strict uRPF supports two options: allow self-ping and allow default. The self-ping option allows the source of the packet to ping itself. The allow default option allows the lookup result to match a default routing entry. When the allow default option is enabled with the strict mode of the uRPF, the packet is processed further only if it arrived through the default interface.

BGP Attributes Download

The BGP Attributes Download feature enables you to display the installed BGP attributes in CEF. Configure the show cef bgp-attribute command to display the installed BGP attributes in CEF. You can use the show cef bgp-attribute attribute-id command and the show cef bgp-attribute local-attribute-id command to look at specific BGP attributes by attribute ID and local attribute ID.

How to Implement CEF

This section contains instructions for the following tasks:

Verifying CEF

This task allows you to verify CEF.

SUMMARY STEPS

    1.    show cef {ipv4 | ipv6}

    2.    show cef {ipv4 | ipv6} summary

    3.    show cef {ipv4 | ipv6} detail

    4.    show adjacency detail


DETAILED STEPS
      Command or Action Purpose
    Step 1 show cef {ipv4 | ipv6}


    Example:
    RP/0/RSP0/CPU0:router# show cef ipv4
    
     

    Displays the IPv4 or IPv6 CEF table. The next hop and forwarding interface are displayed for each prefix.

    Note   

    The output of the show cef command varies by location.

     
    Step 2 show cef {ipv4 | ipv6} summary


    Example:
    RP/0/RSP0/CPU0:router# show cef ipv4 summary
    
     

    Displays a summary of the IPv4 or IPv6 CEF table.

     
    Step 3 show cef {ipv4 | ipv6} detail


    Example:
    RP/0/RSP0/CPU0:router# show cef ipv4 detail
    
     

    Displays detailed IPv4 or IPv6 CEF table information.

     
    Step 4 show adjacency detail


    Example:
    RP/0/RSP0/CPU0:router# show adjacency detail
    
     

    Displays detailed adjacency information, including Layer 2 information for each interface.

    Note   

    The output of the show adjacency command varies by location.

     

    Configuring BGP Policy Accounting

    This task allows you to configure BGP policy accounting.


    Note


    There are two types of route policies. BGP policy accounting uses the type that is used to set up a traffic index for the BGP prefixes. The route policy is applied to the global BGP IPv4 address family to set up the traffic index when the BGP routes are inserted into the RIB table.


    BGP policy accounting enables per interface accounting for ingress and egress IP traffic based on the traffic index assigned to the source IP address (BGP prefix) and destination IP address (BGP prefix). The traffic index of BGP prefixes can be assigned according to the following parameters using Routing Policy Language (RPL):

    • prefix-set
    • AS-path-set
    • community-set

    Note


    BGP policy accounting is supported on IPv4 prefixes only.


    Two configuration tasks provide the ability to classify BGP prefixes that are in the RIB according to the prefix-set, AS-path-set, or the community-set parameters:

    1. Use the route-policy command to define the policy for traffic index setup based on the prefix-set, AS-path-set, or community-set.
    2. Use the BGP table-policy command to apply the defined route policy to the global BGP IPv4 unicast address family.

    See the Cisco ASR 9000 Series Aggregation Services Router Routing Command Reference for information on the route-policy and table-policy commands.

    BGP policy accounting can be enabled on each interface with the following options:

    • Use the ipv4 bgp policy accounting command with one of the following keyword options:
      • input source-accounting
      • input destination-accounting
      • input source-accounting destination-accounting
    • Use the ipv4 bgp policy accounting command with one of the following keyword options:
      • output source-accounting
      • output destination-accounting
      • output source-accounting destination-accounting
    • Use any combination of the keywords provided for the ipv4 bgp policy accounting command.
    Before You Begin

    Before using the BGP policy accounting feature, you must enable BGP on the router (CEF is enabled by default). See the Cisco ASR 9000 Series Aggregation Services Router Routing Configuration Guide for information on enabling BGP.

    SUMMARY STEPS

      1.    configure

      2.    as-path-set

      3.    exit

      4.    prefix-set name

      5.    exit

      6.    route-policy policy-name

      7.    end

      8.    configure

      9.    router bgp autonomous-system-number

      10.    address-family ipv4 {unicast | multicast }

      11.    table policy policy-name

      12.    end

      13.    configure

      14.    interface type interface-path-id

      15.    ipv4 bgp policy accounting {input | output {destination-accounting [source-accounting] | source-accounting [destination-accounting]}}

      16.    Do one of the following:

      • end
      • commit


    DETAILED STEPS
        Command or Action Purpose
      Step 1 configure


      Example:
      RP/0/RSP0/CPU0:router# configure
       

      Enters global configuration mode.

       
      Step 2 as-path-set


      Example:
      RP/0/RSP0/CPU0:router(config)# as-path-set as107
      RP/0/RSP0/CPU0:router(config-as)# ios-regex '107$'
      RP/0/RSP0/CPU0:router(config-as)# end-set
      
      RP/0/RSP0/CPU0:router(config)# as-path-set as108
      RP/0/RSP0/CPU0:router(config-as)# ios-regex '108$'
      RP/0/RSP0/CPU0:router(config-as)# end-set
      
       

      Enters policy configuration mode.

       
      Step 3 exit


      Example:
      RP/0/RSP0/CPU0:router(config-as)# exit
       

      Returns to global configuration mode.

       
      Step 4 prefix-set name


      Example:
      RP/0/RSP0/CPU0:router(config)# prefix-set RT-65
      
       

      Defines the prefix list.

       
      Step 5 exit


      Example:
      RP/0/RSP0/CPU0:router(config-pfx)# exit
       

      Returns to global configuration mode.

       
      Step 6 route-policy policy-name


      Example:
      RP/0/RSP0/CPU0:router(config)# route-policy rp501b
      
       

      Specifies the route-policy name.

       
      Step 7 end


      Example:
      RP/0/RSP0/CPU0:router(config-rpl)# end
       

      Saves configuration changes.

      • When you issue the end command, the system prompts you to commit changes:
        Uncommitted changes found, commit them before exiting(yes/no/cancel)?[cancel]:
        
        • Entering yes saves configuration changes to the running configuration file, exits the configuration session, and returns the router to EXEC mode.
        • Entering no exits the configuration session and returns the router to EXEC mode without committing the configuration changes.
        • Entering cancel leaves the router in the current configuration session without exiting or committing the configuration changes.
       
      Step 8 configure


      Example:
      RP/0/RSP0/CPU0:router# configure
       

      Enters global configuration mode.

       
      Step 9 router bgp autonomous-system-number


      Example:
      RP/0/RSP0/CPU0:router(config)# router bgp 1
      
       

      Allows you to configure the BGP routing process.

       
      Step 10 address-family ipv4 {unicast | multicast }


      Example:
      RP/0/RSP0/CPU0:router(config-bgp)# address-family ipv4 unicast
      
       

      Allows you to enter the address family configuration mode while configuring a BGP routing session.

       
      Step 11 table policy policy-name


      Example:
      RP/0/RSP0/CPU0:router(config-bgp-af)# table-policy set-traffic-index
      
       

      Applies a routing policy to routes being installed into the routing table.

       
      Step 12 end


      Example:
      RP/0/RSP0/CPU0:router(config-bgp-af)# end
       

      Saves configuration changes.

      • When you issue the end command, the system prompts you to commit changes:
        		Uncommitted changes found, commit them before exiting(yes/no/cancel)?[cancel]:
        		
        		
        • Entering yes saves configuration changes to the running configuration file, exits the configuration session, and returns the router to EXEC mode.
        • Entering no exits the configuration session and returns the router to EXEC mode without committing the configuration changes.
        • Entering cancel leaves the router in the current configuration session without exiting or committing the configuration changes.
       
      Step 13 configure


      Example:
      RP/0/RSP0/CPU0:router# configure
       

      Enters global configuration mode.

       
      Step 14 interface type interface-path-id


      Example:
      RP/0/RSP0/CPU0:router(config)# interface TenGigE0/1/0/2
      
       

      Enters interface configuration mode.

       
      Step 15 ipv4 bgp policy accounting {input | output {destination-accounting [source-accounting] | source-accounting [destination-accounting]}}


      Example:
      RP/0/RSP0/CPU0:router(config-if)# ipv4 bgp policy accounting output destination-accounting
      
       

      Enables BGP policy accounting.

       
      Step 16 Do one of the following:
      • end
      • commit


      Example:
      RP/0/RSP0/CPU0:router(config-if)# end

      or

      RP/0/RSP0/CPU0:router(config-if)# commit
       

      Saves configuration changes.

      • When you issue the end command, the system prompts you to commit changes:
        		Uncommitted changes found, commit them before exiting(yes/no/cancel)?[cancel]:
        		
        		
        • Entering yes saves configuration changes to the running configuration file, exits the configuration session, and returns the router to EXEC mode.
        • Entering no exits the configuration session and returns the router to EXEC mode without committing the configuration changes.
        • Entering cancel leaves the router in the current configuration session without exiting or committing the configuration changes.
      • Use the commit command to save the configuration changes to the running configuration file and remain within the configuration session.
       

      Verifying BGP Policy Accounting

      This task allows you to verify BGP policy accounting.


      Note


      BGP policy accounting is supported on IPv4 prefixes.


      Before You Begin

      BGP policy accounting must be configured. See the Configuring BGP Policy Accounting.

      SUMMARY STEPS

        1.    show route bgp

        2.    show bgp summary

        3.    show bgp ip-address

        4.    show route ipv4 ip-address

        5.    show cef ipv4 prefix

        6.    show cef ipv4 prefix detail

        7.    show cef ipv4 interface type interface-path-id bgp-policy-statistics


      DETAILED STEPS
          Command or Action Purpose
        Step 1 show route bgp


        Example:
        RP/0/RSP0/CPU0:router# show route bgp
        
         

        Displays all BGP routes with traffic indexes.

         
        Step 2 show bgp summary


        Example:
        RP/0/RSP0/CPU0:router# show bgp summary
        
         

        Displays the status of all BGP neighbors.

         
        Step 3 show bgp ip-address


        Example:
        RP/0/RSP0/CPU0:router# show bgp 40.1.1.1
        
         

        Displays BGP prefixes with BGP attributes.

         
        Step 4 show route ipv4 ip-address


        Example:
        RP/0/RSP0/CPU0:router# show route ipv4 40.1.1.1
        
         

        Displays the specific BGP route with the traffic index in the RIB.

         
        Step 5 show cef ipv4 prefix


        Example:
        RP/0/RSP0/CPU0:router# show cef ipv4 40.1.1.1
        
         

        Displays the specific BGP prefix with the traffic index in the RP FIB.

         
        Step 6 show cef ipv4 prefix detail


        Example:
        RP/0/RSP0/CPU0:router# show cef ipv4 40.1.1.1 detail
        
         

        Displays the specific BGP prefix with detailed information in the RP FIB.

         
        Step 7 show cef ipv4 interface type interface-path-id bgp-policy-statistics


        Example:
        RP/0/RSP0/CPU0:router# show cef ipv4 interface TenGigE 0/2/0/4 bgp-policy-statistics
        
         

        Displays the BGP Policy Accounting statistics for the specific interface.

         

        Configuring a Route Purge Delay

        This task allows you to configure a route purge delay. A purge delay purges routes when the RIB or other related process experiences a failure.

        SUMMARY STEPS

          1.    configure

          2.    cef purge-delay seconds

          3.    Use one of these commands:

          • end
          • commit


        DETAILED STEPS
            Command or Action Purpose
          Step 1 configure


          Example:
          RP/0/RSP0/CPU0:router# configure
           

          Enters global configuration mode.

           
          Step 2 cef purge-delay seconds


          Example:
          RP/0/RSP0/CPU0:router(config)# cef purge-delay 180
          
           

          Configures a delay in purging routes when the Routing Information Base (RIB) or other related processes experience a failure.

           
          Step 3 Use one of these commands:
          • end
          • commit


          Example:
          RP/0/RSP0/CPU0:router(config)# end

          or

          RP/0/RSP0/CPU0:router(config)# commit
           

          Saves configuration changes.

          • When you issue the end command, the system prompts you to commit changes:
            Uncommitted changes found, commit them
            before exiting(yes/no/cancel)? [cancel]:
            
            • Entering yes saves configuration changes to the running configuration file, exits the configuration session, and returns the router to EXEC mode.
            • Entering no exits the configuration session and returns the router to EXEC mode without committing the configuration changes.
            • Entering cancel leaves the router in the current configuration session without exiting or committing the configuration changes.
          • Use the commit command to save the configuration changes to the running configuration file, and remain within the configuration session.
           

          Configuring Unicast RPF Checking

          This task allows you to configure unicast Reverse Path Forwarding (uRPF) RPF checking. Unicast RPF checking allows you to mitigate problems caused by malformed or forged (spoofed) IP source addresses that pass through a router. Malformed or forged source addresses can indicate denial-of-service (DoS) attacks based on source IP address spoofing.

          SUMMARY STEPS

            1.    configure

            2.    interface type interface-path-id

            3.    {ipv4 | ipv6} verify unicast source reachable-via {any | rx} [allow-default] [allow-self-ping]

            4.    Do one of the following:

            • end
            • or
            • commit


          DETAILED STEPS
              Command or Action Purpose
            Step 1 configure


            Example:
            RP/0/RSP0/CPU0:router# configure
             

            Enters global configuration mode.

             
            Step 2 interface type interface-path-id


            Example:
            RP/0/RSP0/CPU0:router(config)# interface gigabitethernet 0/1/0/0 
            
             

            Enters interface configuration mode.

             
            Step 3 {ipv4 | ipv6} verify unicast source reachable-via {any | rx} [allow-default] [allow-self-ping]


            Example:
            RP/0/RSP0/CPU0:router(config-if)# ipv4 verify unicast source reachable-via rx
            
             

            Enables IPv4 or IPv6 uRPF checking.

            • The rx keyword enables strict unicast RPF checking. If strict unicast RPF is enabled, a packet is not forwarded unless its source prefix exists in the routing table and the output interface matches the interface on which the packet was received.
            • The allow-default keyword enables the matching of default routes. This option applies to both loose and strict RPF.
            • The allow-self-ping keyword enables the router to ping out an interface. This option applies to both loose and strict RPF.
             
            Step 4 Do one of the following:
            • end
            • or
            • commit


            Example:
            RP/0/RSP0/CPU0:router(config-if)# end

            or

            RP/0/RSP0/CPU0:router(config-if)# commit
             

            Saves configuration changes.

            • When you issue the end command, the system prompts you to commit changes:
              		Uncommitted changes found, commit them before exiting(yes/no/cancel)?[cancel]:
              		
              		
              • Entering yes saves configuration changes to the running configuration file, exits the configuration session, and returns the router to EXEC mode.
              • Entering no exits the configuration session and returns the router to EXEC mode without committing the configuration changes.
              • Entering cancel leaves the router in the current configuration session without exiting or committing the configuration changes.
            • Use the commit command to save the configuration changes to the running configuration file and remain within the configuration session.
             

            Configuring Modular Services Card-to-Route Processor Management Ethernet Interface Switching

            This task allows you to enable MSC-to-RP management Ethernet interface switching.

            SUMMARY STEPS

              1.    configure

              2.    rp mgmtethernet forwarding

              3.    Use one of these commands:

              • end
              • commit


            DETAILED STEPS
                Command or Action Purpose
              Step 1 configure


              Example:
              RP/0/RSP0/CPU0:router# configure
               

              Enters global configuration mode.

               
              Step 2 rp mgmtethernet forwarding


              Example:
              RP/0/RSP0/CPU0:router(config)# rp mgmtethernet forwarding
              
               

              Enables switching from the MSC to the route processor Management Ethernet interfaces.

               
              Step 3 Use one of these commands:
              • end
              • commit


              Example:
              RP/0/RSP0/CPU0:router(config)# end

              or

              RP/0/RSP0/CPU0:router(config)# commit
               

              Saves configuration changes.

              • When you issue the end command, the system prompts you to commit changes:
                Uncommitted changes found, commit them
                before exiting(yes/no/cancel)? [cancel]:
                
                • Entering yes saves configuration changes to the running configuration file, exits the configuration session, and returns the router to EXEC mode.
                • Entering no exits the configuration session and returns the router to EXEC mode without committing the configuration changes.
                • Entering cancel leaves the router in the current configuration session without exiting or committing the configuration changes.
              • Use the commit command to save the configuration changes to the running configuration file, and remain within the configuration session.
               

              Configuring BGP Attributes Download

              This task allows you to configure the BGP Attributes Download feature.

              Configuring BGP Attributes Download

              SUMMARY STEPS

                1.    configure

                2.    cef bgp attribute {attribute-id | local-attribute-id }

                3.    Use one of these commands:

                • end
                • commit


              DETAILED STEPS
                  Command or Action Purpose
                Step 1 configure


                Example:
                RP/0/RSP0/CPU0:router# configure
                 

                Enters global configuration mode.

                 
                Step 2 cef bgp attribute {attribute-id | local-attribute-id }


                Example:
                RP/0/RSP0/CPU0:router(config)# cef bgp attribute 508
                
                 

                Configures a CEF BGP attribute.

                 
                Step 3 Use one of these commands:
                • end
                • commit


                Example:
                RP/0/RSP0/CPU0:router(config)# end

                or

                RP/0/RSP0/CPU0:router(config)# commit
                 

                Saves configuration changes.

                • When you issue the end command, the system prompts you to commit changes:
                  Uncommitted changes found, commit them
                  before exiting(yes/no/cancel)? [cancel]:
                  
                  • Entering yes saves configuration changes to the running configuration file, exits the configuration session, and returns the router to EXEC mode.
                  • Entering no exits the configuration session and returns the router to EXEC mode without committing the configuration changes.
                  • Entering cancel leaves the router in the current configuration session without exiting or committing the configuration changes.
                • Use the commit command to save the configuration changes to the running configuration file, and remain within the configuration session.
                 

                Configuration Examples for Implementing CEF on Routers Software

                This section provides the following configuration examples:

                Configuring BGP Policy Accounting: Example

                The following example shows how to configure BGP policy accounting.

                Configure loopback interfaces for BGP router-id:

                interface Loopback1
                ipv4 address 10
                .1.1.1 255.255.255.255
                

                Configure interfaces with the BGP policy accounting options:

                interface TenGigE0/2/0/2
                 mtu 1514
                 ipv4 address 10
                .1.0.1 255.255.255.0
                 proxy-arp
                 ipv4 directed-broadcast
                 ipv4 bgp policy accounting input source-accounting destination-accounting
                 ipv4 bgp policy accounting output source-accounting destination-accounting
                !
                interface TenGigE0/2/0/2.1
                 ipv4 address 10
                .1.1.1 255.255.255.0
                 ipv4 bgp policy accounting input source-accounting destination-accounting
                 ipv4 bgp policy accounting output source-accounting destination-accounting
                 dot1q vlan 1
                !
                interface TenGigE0/2/0/4
                 mtu 1514
                 ipv4 address 10
                .1.0.1 255.255.255.0
                 proxy-arp
                 ipv4 directed-broadcast
                 ipv4 bgp policy accounting input source-accounting destination-accounting
                 ipv4 bgp policy accounting output source-accounting destination-accounting
                !
                interface TenGigE0/2/0/4.1
                 ipv4 address 10
                .1.2
                .1 255.255.255.0
                 ipv4 bgp policy accounting input source-accounting destination-accounting
                 ipv4 bgp policy accounting output source-accounting destination-accounting
                 dot1q vlan 1
                !
                interface gigabitethernet 0/0/0/4
                 mtu 4474
                 ipv4 address 10
                .1.0.40 
                255.255.0.0
                 ipv4 directed-broadcast
                 ipv4 bgp policy accounting input source-accounting destination-accounting
                 ipv4 bgp policy accounting output source-accounting destination-accounting
                 encapsulation ppp
                 gigabitethernet
                  crc 32
                 !
                 keepalive disable
                !
                interface gigabitethernet0/0/0/8
                 mtu 4474
                 ipv4 address 18
                .8
                .0.1 255.255.0.0
                 ipv4 directed-broadcast
                 ipv4 bgp policy accounting input source-accounting destination-accounting
                 ipv4 bgp policy accounting output source-accounting destination-accounting
                 gigabitethernet
                  crc 32
                 !
                 keepalive disable
                !
                

                Configure controller:

                controller gigabitethernet0/0/0/4
                 ais-shut
                 path
                  ais-shut
                 !
                 threshold sf-ber 5
                !
                controller SONET0/0/0/8
                 ais-shut
                 path
                  ais-shut
                 !
                 threshold sf-ber 5
                !
                

                Configure AS-path-set and prefix-set:

                as-path-set as107
                  ios-regex '107$'
                end-set
                
                as-path-set as108
                  ios-regex '108$'
                end-set
                
                prefix-set RT-65.0
                  65.0.0.0/16 ge 16 le 32
                end-set
                
                prefix-set RT-66.0
                  66.0.0.0/16 ge 16 le 32
                end-set
                

                Configure the route-policy (table-policy) to set up the traffic indexes based on each prefix, AS-path-set, and prefix-set:

                route-policy bpa1
                
                  if destination in  (10
                .1.1.0/24) then
                    set traffic-index 1
                  elseif destination in  (10
                .1.2.0/24) then
                    set traffic-index 2
                  elseif destination in  (10
                .1.3.0/24) then
                    set traffic-index 3
                  elseif destination in  (10
                .1.4.0/24) then
                    set traffic-index 4
                  elseif destination in  (10
                .1.5.0/24) then
                    set traffic-index 5
                  endif
                
                  if destination in  (10
                .1.1.0/24) then
                    set traffic-index 6
                  elseif destination in  (10
                .1.2.0/24) then
                    set traffic-index 7
                  elseif destination in  (10
                .1.3.0/24) then
                    set traffic-index 8
                  elseif destination in  (10
                .1.4.0/24) then
                    set traffic-index 9
                  elseif destination in  (10
                .1.5.0/24) then
                    set traffic-index 10
                  endif
                
                  if as-path in as107 then
                       set traffic-index 7
                  elseif as-path in as108 then
                       set traffic-index 8
                  endif
                
                  if destination in RT-65.0 then
                     set traffic-index 15
                  elseif destination in RT-66.0 then
                     set traffic-index 16
                  endif
                
                end-policy
                

                Configure the regular BGP route-policy to pass or drop all the BGP routes:

                route-policy drop-all
                  drop
                end-policy
                !
                route-policy pass-all
                  pass
                end-policy
                !
                

                Configure the BGP router and apply the table-policy to the global ipv4 address family:

                router bgp 100
                 bgp router-id Loopback1
                 bgp graceful-restart
                 bgp as-path-loopcheck
                 address-family ipv4 unicast
                  table-policy bpa1
                  maximum-paths 8
                  bgp dampening
                 !
                

                Configure the BGP neighbor-group:

                neighbor-group ebgp-peer-using-int-addr
                  address-family ipv4 unicast
                   policy pass-all in
                   policy drop-all out
                  !
                 !
                 neighbor-group ebgp-peer-using-int-addr-121
                  remote-as 121
                  address-family ipv4 unicast
                   policy pass-all in
                   policy drop-all out
                  !
                 !
                 neighbor-group ebgp-peer-using-int-addr-pass-out
                  address-family ipv4 unicast
                   policy pass-all in
                   policy pass-all out
                  !
                 !
                

                Configure BGP neighbors:

                neighbor 10
                .4
                .0.2
                  remote-as 107
                  use neighbor-group ebgp-peer-using-int-addr
                 !
                 neighbor 10
                .8
                .0.2
                  remote-as 108
                  use neighbor-group ebgp-peer-using-int-addr
                 !
                 neighbor 10
                .7
                .0.2
                  use neighbor-group ebgp-peer-using-int-addr-121
                 !
                 neighbor 10
                .1.7
                .2
                  use neighbor-group ebgp-peer-using-int-addr-121
                 !
                neighbor 10
                .18
                .0.2
                  remote-as 122
                  use neighbor-group ebgp-peer-using-int-addr
                 !
                 neighbor 10
                .18
                .1.2
                  remote-as 1221
                  use neighbor-group ebgp-peer-using-int-addr
                 !
                end
                

                Verifying BGP Policy Statistics: Example

                The following example shows how to verify the traffic index setup for each BGP prefix and BGP Policy Accounting statistics on ingress and egress interfaces. The following traffic stream is configured for this example:

                • Traffic comes in from TenGigE0/2/0/4 and goes out to 5 VLAN subinterfaces under TenGigE0/2/0/2
                • Traffic comes in from GigabitEthernet 0/0/08 and goes out to GigabitEthernet 0/0/0/4
                show cef ipv4 interface gigabitethernet 0/0/0/8 bgp-policy-statistics
                
                gigabitethernet0/0/0/8 is up 
                Input BGP policy accounting on dst IP address enabled
                  buckets      packets       bytes
                  7            5001160   500116000
                  15          10002320  1000232000
                Input BGP policy accounting on src IP address enabled
                  buckets      packets       bytes
                  8            5001160   500116000
                  16          10002320  1000232000
                Output BGP policy accounting on dst IP address enabled
                  buckets      packets       bytes
                  0                 15         790
                Output BGP policy accounting on src IP address enabled
                  buckets      packets       bytes
                  0                 15         790
                
                show cef ipv4 interface gigabitethernet 0/0/0/4 bgp-policy-statistics
                
                gigabitethernet0/0/0/4 is up 
                Input BGP policy accounting on dst IP address enabled
                  buckets      packets       bytes
                Input BGP policy accounting on src IP address enabled
                  buckets      packets       bytes
                Output BGP policy accounting on dst IP address enabled
                  buckets      packets       bytes
                  0                 13         653
                  7            5001160   500116000
                  15          10002320  1000232000
                Output BGP policy accounting on src IP address enabled
                  buckets      packets       bytes
                  0                 13         653
                  8            5001160   500116000
                  16          10002320  1000232000
                
                show cef ipv4 interface TenGigE0/2/0/4 bgp-policy-statistics 
                
                TenGigE0/2/0/4 is up 
                Input BGP policy accounting on dst IP address enabled
                  buckets      packets       bytes
                  1            3297102   329710200
                  2            3297102   329710200
                  3            3297102   329710200
                  4            3297101   329710100
                  5            3297101   329710100
                Input BGP policy accounting on src IP address enabled
                  buckets      packets       bytes
                  6            3297102   329710200
                  7            3297102   329710200
                  8            3297102   329710200
                  9            3297101   329710100
                  10           3297101   329710100
                Output BGP policy accounting on dst IP address enabled
                  buckets      packets       bytes
                  0                 15         733
                Output BGP policy accounting on src IP address enabled
                  buckets      packets       bytes
                  0                 15         733
                
                show cef ipv4 interface TenGigE0/2/0/2.1 bgp-policy-statistics
                
                TenGigE0/2/0/2.1 is up 
                Input BGP policy accounting on dst IP address enabled
                  buckets      packets       bytes
                Input BGP policy accounting on src IP address enabled
                  buckets      packets       bytes
                Output BGP policy accounting on dst IP address enabled
                  buckets      packets       bytes
                  0                 15         752
                  1            3297102   329710200
                  2            3297102   329710200
                  3            3297102   329710200
                  4            3297101   329710100
                  5            3297101   329710100
                Output BGP policy accounting on src IP address enabled
                  buckets      packets       bytes
                  0                 15         752
                  6            3297102   329710200
                  7            3297102   329710200
                  8            3297102   329710200
                  9            3297101   329710100
                  10           3297101   329710100
                

                The following example show how to verify BGP routes and traffic indexes:

                show route bgp
                
                B     10
                .1.1.0/24 [20/0] via 10
                .17
                .1.2, 00:07:09
                      Traffic Index 1
                B     10
                .1.2.0/24 [20/0] via 10
                .17
                .1.2, 00:07:09
                      Traffic Index 2
                B    10
                .1.3.0/24 [20/0] via 10
                .17
                .1.2, 00:07:09
                      Traffic Index 3
                B    10
                .1.4.0/24 [20/0] via 10
                .17
                .1.2, 00:07:09
                      Traffic Index 4
                B    10
                .1.5.0/24 [20/0] via 10
                .17
                .1.2, 00:07:09
                      Traffic Index 5
                B    10
                .18
                .1.0/24 [20/0] via 10
                .18
                .1.2, 00:07:09
                      Traffic Index 6
                B    10
                .18
                .2.0/24 [20/0] via 10
                .18
                .1.2, 00:07:09
                      Traffic Index 7
                B    10
                .18
                .3.0/24 [20/0] via 10
                .18
                .1.2, 00:07:09
                      Traffic Index 8
                B    10
                .28
                .4.0/24 [20/0] via 10
                .18
                .1.2, 00:07:09
                      Traffic Index 9
                B    10
                .28
                .5.0/24 [20/0] via 10
                .18
                .1.2, 00:07:09
                      Traffic Index 10
                B    10
                .65
                .1.0/24 [20/0] via 10
                .45
                .0.2, 00:07:09
                      Traffic Index 15
                B    10
                .65
                .2.0/24 [20/0] via 10
                .45
                .0.2, 00:07:09
                      Traffic Index 15
                B    10
                .65
                .3.0/24 [20/0] via 10
                .45
                .0.2, 00:07:09
                      Traffic Index 15
                B    10
                .65
                .65
                .0/24 [20/0] via 10
                .45
                .0.2, 00:07:09
                      Traffic Index 15
                B    10
                .65
                .5.0/24 [20/0] via 10
                .45
                .0.2, 00:07:09
                      Traffic Index 15
                B    10
                .65
                .6.0/24 [20/0] via 10
                .45
                .0.2, 00:07:09
                      Traffic Index 15
                B    10
                .65
                .7.0/24 [20/0] via 10
                .45
                .0.2, 00:07:09
                      Traffic Index 15
                B    10
                .65
                .8.0/24 [20/0] via 10
                .45
                .0.2, 00:07:09
                      Traffic Index 15
                B    10
                .65
                .9.0/24 [20/0] via 10
                .45
                .0.2, 00:07:09
                      Traffic Index 15
                B    10
                .65
                .10.0/24 [20/0] via 10
                .45
                .0.2, 00:07:09
                      Traffic Index 15
                B    10
                .66
                .1.0/24 [20/0] via 10
                .32
                .0.2, 00:07:09
                      Traffic Index 16
                B    10
                .66
                .2.0/24 [20/0] via 10
                .32
                .0.2, 00:07:09
                      Traffic Index 16
                B    10
                .66
                .3.0/24 [20/0] via 10
                .32
                .0.2, 00:07:09
                      Traffic Index 16
                B    10
                .66
                .4.0/24 [20/0] via 10
                .32
                .0.2, 00:07:09
                      Traffic Index 16
                B    10
                .66
                .5.0/24 [20/0] via 10
                .32
                .0.2, 00:07:09
                      Traffic Index 16
                B    10
                .66
                .6.0/24 [20/0] via 10
                .32
                .0.2, 00:07:09
                      Traffic Index 16
                B    10
                .66
                .7.0/24 [20/0] via 10
                .32
                .0.2, 00:07:09
                      Traffic Index 16
                B    10
                .66
                .8.0/24 [20/0] via 10
                .32
                .0.2, 00:07:09
                      Traffic Index 16
                B    10
                .66
                .9.0/24 [20/0] via 10
                .32
                .0.2, 00:07:09
                      Traffic Index 16
                B    10
                .66
                .10.0/24 [20/0] via 10
                .32
                .0.2, 00:07:09
                      Traffic Index 16
                B    10
                .67
                .1.0/24 [20/0] via 10
                .32
                .0.2, 00:07:09
                      Traffic Index 7
                B    10
                .67
                .2.0/24 [20/0] via 10
                .32
                .0.2, 00:07:09
                      Traffic Index 7
                B    10
                .67
                .3.0/24 [20/0] via 10
                .32
                .0.2, 00:07:09
                      Traffic Index 7
                B    10
                .67
                .4.0/24 [20/0] via 10
                .32
                .0.2, 00:07:09
                      Traffic Index 7
                B    10
                .67
                .5.0/24 [20/0] via 10
                .32
                .0.2, 00:07:09
                      Traffic Index 7
                B    10
                .67
                .6.0/24 [20/0] via 10
                .32
                .0.2, 00:07:09
                      Traffic Index 7
                B    10
                .67
                .7.0/24 [20/0] via 10
                .32
                .0.2, 00:07:09
                      Traffic Index 7
                B    10
                .67
                .8.0/24 [20/0] via 10
                .32
                .0.2, 00:07:09
                      Traffic Index 7
                B    10
                .67
                .9.0/24 [20/0] via 10
                .32
                .0.2, 00:07:09
                      Traffic Index 7
                B    10
                .67
                .10.0/24 [20/0] via 10
                .32
                .0.2, 00:07:09
                      Traffic Index 7
                B    10
                .68
                .1.0/24 [20/0] via 10
                .8
                .0.2, 00:07:09
                      Traffic Index 8
                B    10
                .68
                .2.0/24 [20/0] via 10
                .8
                .0.2, 00:07:09
                      Traffic Index 8
                B    10
                .68
                .3.0/24 [20/0] via 10
                .8
                .0.2, 00:07:09
                      Traffic Index 8
                B    10
                .68
                .4.0/24 [20/0] via 10
                .8
                .0.2, 00:07:09
                      Traffic Index 8
                B    10
                .68
                .5.0/24 [20/0] via 10
                .8
                .0.2, 00:07:09
                      Traffic Index 8
                B    10
                .68
                .6.0/24 [20/0] via 10
                .8
                .0.2, 00:07:09
                      Traffic Index 8
                B    10
                .68
                .7.0/24 [20/0] via 10
                .8
                .0.2, 00:07:09
                      Traffic Index 8
                B    10
                .68
                .8.0/24 [20/0] via 10
                .8
                .0.2, 00:07:09
                      Traffic Index 8
                B    10
                .68
                .9.0/24 [20/0] via 10
                .8
                .0.2, 00:07:09
                      Traffic Index 8
                B    10
                .68
                .10.0/24 [20/0] via 10
                .8
                .0.2, 00:07:09
                      Traffic Index 8
                
                show bgp summary
                
                BGP router identifier 192
                .0
                .2
                .0
                , local AS number 100
                BGP generic scan interval 60 secs
                BGP main routing table version 151
                Dampening enabled
                BGP scan interval 60 secs
                BGP is operating in STANDALONE mode.
                
                Process         RecvTblVer    bRIB/RIB  SendTblVer
                Speaker                151         151         151
                
                Neighbor        Spk    AS MsgRcvd MsgSent   TblVer  InQ OutQ Up/Down  St/PfxRcd
                10
                .4
                .0.2                    0     107      54      53      151    0    0 00:25:26       20
                10
                .1.0.2                    0   108      54      53      151    0    0 00:25:28       20
                10
                .1.0.2          0   121      53      54      151    0    0 00:25:42        0
                10
                .1.1.2          0   121      53      53      151    0    0 00:25:06        5
                10
                .1.2.2          0   121      52      54      151    0    0 00:25:04        0
                10
                .1.3.2          0   121      52      53      151    0    0 00:25:26        0
                10
                .1.4.2          0   121      53      54      151    0    0 00:25:41        0
                10
                .1.5.2          0   121      53      54      151    0    0 00:25:43        0
                10
                .1.6.2          0   121      51      53      151    0    0 00:24:59        0
                10
                .1.7.2          0   121      51      52      151    0    0 00:24:44        0
                10
                .1.8.2          0   121      51      52      151    0    0 00:24:49        0
                10
                .2
                .0.2          0   122      52      54      151    0    0 00:25:21        0
                10
                .2
                .1.2          0  1221      54      54      151    0    0 00:25:43        5
                10
                .2
                .2.2          0  1222      53      54      151    0    0 00:25:38        0
                10
                .2
                .3.2          0  1223      52      53      151    0    0 00:25:17        0
                10
                .2
                .4.2          0  1224      51      52      151    0    0 00:24:57        0
                10
                .2
                .5.2          0  1225      52      53      151    0    0 00:25:14        0
                10
                .2
                .6.2          0  1226      52      54      151    0    0 00:25:04        0
                10
                .2
                .7.2          0  1227      52      54      151    0    0 00:25:13        0
                10
                .2
                .8.2          0  1228      53      54      151    0    0 00:25:36        0
                
                show bgp 27.1.1.1
                
                BGP routing table entry for 27.1.1.0/24
                Versions:
                  Process           bRIB/RIB  SendTblVer
                  Speaker                102         102
                Paths: (1 available, best #1)
                  Not advertised to any peer
                  Received by speaker 0
                  121
                    10
                .1.1.2 from 10
                .1.1.2 (10
                .1.1.2)
                      Origin incomplete, localpref 100, valid, external, best
                      Community: 27:1 121:1
                
                show bgp 10
                .1.1.1
                
                BGP routing table entry for 10
                .1.1.0/24
                Versions:
                  Process           bRIB/RIB  SendTblVer
                  Speaker                107         107
                Paths: (1 available, best #1)
                  Not advertised to any peer
                  Received by speaker 0
                  1221
                      10
                .2
                .1.2 from 10
                .2
                .1.2 (18.1.1.2)
                      Origin incomplete, localpref 100, valid, external, best
                      Community: 28:1 1221:1
                
                show bgp 10
                .0.1.1
                
                BGP routing table entry for 10
                .0.1.0/24
                Versions:
                  Process           bRIB/RIB  SendTblVer
                  Speaker                112         112
                Paths: (1 available, best #1)
                  Not advertised to any peer
                  Received by speaker 0
                  107
                    10
                .1.0.2 from 10
                .1.0.2 (10
                .1.0.2)
                      Origin incomplete, localpref 100, valid, external, best
                      Community: 107:65
                
                show bgp 10
                .2
                .1.1
                
                BGP routing table entry for 10
                .2
                .1.0/24
                Versions:
                  Process           bRIB/RIB  SendTblVer
                  Speaker                122         122
                Paths: (1 available, best #1)
                  Not advertised to any peer
                  Received by speaker 0
                  108
                    8.1.0.2 from 8.1.0.2 (8.1.0.2)
                      Origin incomplete, localpref 100, valid, external, best
                      Community: 108:66
                
                show bgp 67.0.1.1
                
                BGP routing table entry for 67.0.1.0/24
                Versions:
                  Process           bRIB/RIB  SendTblVer
                  Speaker                132         132
                Paths: (1 available, best #1)
                  Not advertised to any peer
                  Received by speaker 0
                  107
                    4.1.0.2 from 4.1.0.2 (4.1.0.2)
                      Origin incomplete, localpref 100, valid, external, best
                      Community: 107:67
                
                show bgp 68.0.1.1
                
                BGP routing table entry for 68.0.1.0/24
                Versions:
                  Process           bRIB/RIB  SendTblVer
                  Speaker                142         142
                Paths: (1 available, best #1)
                  Not advertised to any peer
                  Received by speaker 0
                  108
                    8.1.0.2 from 8.1.0.2 (8.1.0.2)
                      Origin incomplete, localpref 100, valid, external, best
                      Community: 108:68
                
                show route ipv4 27.1.1.1
                
                Routing entry for 27.1.1.0/24
                  Known via "bgp 100", distance 20, metric 0
                  Tag 121, type external, Traffic Index 1
                  Installed Nov 11 21:14:05.462
                  Routing Descriptor Blocks
                    17.1.1.2, from 17.1.1.2
                      Route metric is 0
                  No advertising protos. 
                
                show route ipv4 28.1.1.1
                
                Routing entry for 28.1.1.0/24
                  Known via "bgp 100", distance 20, metric 0
                  Tag 1221, type external, Traffic Index 6
                  Installed Nov 11 21:14:05.462
                  Routing Descriptor Blocks
                    18.1.1.2, from 18.1.1.2
                      Route metric is 0
                  No advertising protos. 
                
                show route ipv4 65.0.1.1
                
                Routing entry for 65.0.1.0/24
                  Known via "bgp 100", distance 20, metric 0
                  Tag 107, type external, Traffic Index 15
                  Installed Nov 11 21:14:05.462
                  Routing Descriptor Blocks
                    4.1.0.2, from 4.1.0.2
                      Route metric is 0
                  No advertising protos. 
                
                show route ipv4 66.0.1.1
                
                Routing entry for 66.0.1.0/24
                  Known via "bgp 100", distance 20, metric 0
                  Tag 108, type external, Traffic Index 16
                  Installed Nov 11 21:14:05.462
                  Routing Descriptor Blocks
                    8.1.0.2, from 8.1.0.2
                      Route metric is 0
                  No advertising protos. 
                
                show route ipv4 67.0.1.1
                
                Routing entry for 67.0.1.0/24
                  Known via "bgp 100", distance 20, metric 0
                  Tag 107, type external, Traffic Index 7
                  Installed Nov 11 21:14:05.462
                  Routing Descriptor Blocks
                    4.1.0.2, from 4.1.0.2
                      Route metric is 0
                  No advertising protos. 
                
                show route ipv4 68.0.1.1
                
                Routing entry for 68.0.1.0/24
                  Known via "bgp 100", distance 20, metric 0
                  Tag 108, type external, Traffic Index 8
                  Installed Nov 11 21:14:05.462
                  Routing Descriptor Blocks
                    8.1.0.2, from 8.1.0.2
                      Route metric is 0
                  No advertising protos. 
                
                show cef ipv4 27.1.1.1
                
                27.1.1.0/24, version 263, source-destination sharing
                Prefix Len 24, Traffic Index 1, precedence routine (0)
                  via 17.1.1.2, 0 dependencies, recursive
                    next hop 17.1.1.2/24, TenGigE0/2/0/2.1 via 17.1.1.0/24
                    valid remote adjacency
                  Recursive load sharing using 17.1.1.0/24
                
                show cef ipv4 28.1.1.1
                
                28.1.1.0/24, version 218, source-destination sharing
                Prefix Len 24, Traffic Index 6, precedence routine (0)
                  via 18.1.1.2, 0 dependencies, recursive
                    next hop 18.1.1.2/24, TenGigE0/2/0/4.1 via 18.1.1.0/24
                    valid remote adjacency
                  Recursive load sharing using 18.1.1.0/24
                
                show cef ipv4 65.0.1.1
                
                65.0.1.0/24, version 253, source-destination sharing
                Prefix Len 24, Traffic Index 15, precedence routine (0)
                  via 4.1.0.2, 0 dependencies, recursive
                    next hop 4.1.0.2/16, gigabitethernet0/0/0/4 via 4.1.0.0/16
                    valid remote adjacency
                  Recursive load sharing using 4.1.0.0/16
                
                show cef ipv4 66.0.1.1
                
                66.0.1.0/24, version 233, source-destination sharing
                Prefix Len 24, Traffic Index 16, precedence routine (0)
                  via 8.1.0.2, 0 dependencies, recursive
                    next hop 8.1.0.2/16, gigabitethernet 0/0/0/8 via 8.1.0.0/16
                    valid remote adjacency
                  Recursive load sharing using 8.1.0.0/16
                
                show cef ipv4 67.0.1.1
                
                67.0.1.0/24, version 243, source-destination sharing
                Prefix Len 24, Traffic Index 7, precedence routine (0)
                  via 4.1.0.2, 0 dependencies, recursive
                    next hop 4.1.0.2/16, gigabitethernet 0/0/0/4 via 4.1.0.0/16
                    valid remote adjacency
                  Recursive load sharing using 4.1.0.0/16
                
                show cef ipv4 68.0.1.1
                
                68.0.1.0/24, version 223, source-destination sharing
                Prefix Len 24, Traffic Index 8, precedence routine (0)
                  via 8.1.0.2, 0 dependencies, recursive
                    next hop 8.1.0.2/16, gigabitethernet0/0/0/8 via 8.1.0.0/16
                    valid remote adjacency
                  Recursive load sharing using 8.1.0.0/16
                
                show cef ipv4 27.1.1.1 detail
                
                27.1.1.0/24, version 263, source-destination sharing
                Prefix Len 24, Traffic Index 1, precedence routine (0)
                  via 17.1.1.2, 0 dependencies, recursive
                    next hop 17.1.1.2/24, TenGigE0/2/0/2.1 via 17.1.1.0/24
                    valid remote adjacency
                
                  Recursive load sharing using 17.1.1.0/24
                  Load distribution: 0 (refcount 6)
                
                  Hash  OK  Interface                 Address  Packets
                  1     Y   TenGigE0/2/0/2.1          (remote)               0
                
                show cef ipv4 28.1.1.1 detail
                
                28.1.1.0/24, version 218, source-destination sharing
                Prefix Len 24, Traffic Index 6, precedence routine (0)
                  via 18.1.1.2, 0 dependencies, recursive
                    next hop 18.1.1.2/24, TenGigE0/2/0/4.1 via 18.1.1.0/24
                    valid remote adjacency
                
                  Recursive load sharing using 18.1.1.0/24
                  Load distribution: 0 (refcount 6)
                
                  Hash  OK  Interface                 Address  Packets
                  1     Y   TenGigE0/2/0/4.1          (remote)               0
                
                show cef ipv4 65.0.1.1 detail
                
                65.0.1.0/24, version 253, source-destination sharing
                Prefix Len 24, Traffic Index 15, precedence routine (0)
                  via 4.1.0.2, 0 dependencies, recursive
                    next hop 4.1.0.2/16, gigabitethernet0/0/0/4 via 4.1.0.0/16
                    valid remote adjacency
                
                  Recursive load sharing using 4.1.0.0/16
                  Load distribution: 0 (refcount 21)
                
                  Hash  OK  Interface                 Address  Packets
                  1     Y   gigabitethernet0/0/0/4                (remote)               0
                
                show cef ipv4 66.0.1.1 detail
                
                66.0.1.0/24, version 233, source-destination sharing
                Prefix Len 24, Traffic Index 16, precedence routine (0)
                  via 8.1.0.2, 0 dependencies, recursive
                    next hop 8.1.0.2/16, gigabitethernet0/0/0/8 via 8.1.0.0/16
                    valid remote adjacency
                
                  Recursive load sharing using 8.1.0.0/16
                  Load distribution: 0 (refcount 21)
                
                  Hash  OK  Interface                 Address  Packets
                  1     Y   gigabitethernet 0/0/0/8                (remote)               0
                
                show cef ipv4 67.0.1.1 detail
                
                67.0.1.0/24, version 243, source-destination sharing
                Prefix Len 24, Traffic Index 7, precedence routine (0)
                  via 4.1.0.2, 0 dependencies, recursive
                    next hop 4.1.0.2/16, gigabitethernet 0/0/0/4 via 4.1.0.0/16
                    valid remote adjacency
                
                  Recursive load sharing using 4.1.0.0/16
                  Load distribution: 0 (refcount 21)
                
                  Hash  OK  Interface                 Address  Packets
                  1     Y   gigabitethernet 0/0/0/4                (remote)               0
                
                show cef ipv4 68.0.1.1 detail
                
                68.0.1.0/24, version 223, source-destination sharing
                Prefix Len 24, Traffic Index 8, precedence routine (0)
                  via 8.1.0.2, 0 dependencies, recursive
                    next hop 8.1.0.2/16, gigabitethernet 0/0/0/8 via 8.1.0.0/16
                    valid remote adjacency
                
                  Recursive load sharing using 8.1.0.0/16
                  Load distribution: 0 (refcount 21)
                
                  Hash  OK  Interface                 Address  Packets
                  1     Y   gigabitethernet 0/0/0/8                (remote)               0
                

                Configuring Unicast RPF Checking: Example

                The following example shows how to configure unicast RPF checking:

                configure
                interface gigabitethernet 0/0/0/1
                ipv4 verify unicast source reachable-via rx
                end
                

                Configuring the Switching of Modular Services Card to Management Ethernet Interfaces on the Route Processor: Example

                The following example shows how to configure the switching of the MSC to Management Ethernet interfaces on the route processor:

                configure
                rp mgmtethernet forwarding
                end
                

                Configuring BGP Attributes Download: Example

                The following example shows how to configure the BGP Attributes Download feature:

                router configure
                show cef bgp attribute {attribute-id| local-attribute-id}
                

                Additional References

                The following sections provide references related to implementing CEF.

                Related Documents

                Related Topic

                Document Title

                CEF commands: complete command syntax, command modes, command history, defaults, usage guidelines, and examples

                Cisco Express Forwarding Commands module in Cisco ASR 9000 Series Aggregation Services Router IP Addresses and Services Command Reference

                BGP commands: complete command syntax, command modes, command history, defaults, usage guidelines, and examples

                BGP Commands module in the Cisco ASR 9000 Series Aggregation Services Router Routing Command Reference

                Link Bundling Commands: complete command syntax, command modes, command history, defaults, usage guidelines, and examples

                Link Bundling Commands module in the Cisco ASR 9000 Series Aggregation Services Router Interface and Hardware Component Command Reference

                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

                To locate and download MIBs, use the Cisco MIB Locator found at the following URL and choose a platform under the Cisco Access Products menu: http:/​/​cisco.com/​public/​sw-center/​netmgmt/​cmtk/​mibs.shtml

                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