Verifying IP Multicast Operation

This module describes how to verify IP multicast operation in a network after Protocol Independent Multicast (PIM) sparse mode (PIM-SM) or Source Specific Multicast (PIM-SSM) has been implemented. The tasks in this module can be used to test IP multicast reachability and to confirm that receivers and sources are operating as expected in an IP multicast network.

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 Verifying IP Multicast Operation

  • Before performing the tasks in this module, you should be familiar with the concepts described in the “ IP Multicast Technology Overview ” module.

  • The tasks in this module assume that IP multicast has been enabled and that PIM-SM or SSM has been configured using the relevant tasks described in the “ Configuring Basic IP Multicast ” module.

Restrictions for Verifying IP Multicast Operation

  • For PIM-SM, this module assumes that the shortest path tree (SPT) threshold for PIM-enabled routers is set to the value of zero (the default) and not infinity. For more information about setting the SPT threshold, see the ip pim spt-threshold command page in the Cisco IOS IP Multicast Command Reference.

  • Verifying IP multicast operation in a bidirectional PIM (bidir-PIM) network or a PIM-SM network with a finite or infinite SPT threshold is outside the scope of this module.

Information About Verifying IP Multicast Operation

Guidelines for Verifying IP Multicast Operation in a PIM-SM and PIM-SSM Network Environment

When you verify the operation of IP multicast in a PIM-SM network environment or in an PIM-SSM network environment, a useful approach is to begin the verification process on the last hop router, and then continue the verification process on the routers along the SPT until the first hop router has been reached. The goal of the verification is to ensure that IP multicast traffic is being routed properly through an IP multicast network.

Common Commands Used to Verify IP Multicast Operation on the Last Hop Router for PIM-SM and PIM-SSM

The table describes the common commands used to verify IP multicast operation on the last hop router in PIM-SM and PIM-SSM network environments.

Table 1 Common IP Multicast Verification Commands (Last Hop Router)

Command

Description and Purpose

show ip igmp groups

Displays the multicast groups with receivers that are directly connected to the router and that were learned through the Internet Group Management Protocol (IGMP).

  • Use this command to confirm that the IGMP cache is being properly populated on the last hop router for the groups that receivers on the LAN have joined.

show ip pim rp mapping

Displays all group-to-RP mappings of which the router is aware (either configured or learned from Auto-RP or BSR).

  • Use this command to confirm that the group-to-RP mappings are being populated correctly on the last hop router.

Note   

The show ip pim rp mappingcommand does not work with routers in a PIM-SSM network because PIM-SSM does not use rendezvous points (RPs).

show ip mroute

Displays the contents of the multicast routing (mroute) table.

  • Use this command to verify that the mroute table is being populated properly on the last hop router.

show ip interface

Displays information and statistics about configured interfaces.

  • Use this command to verify that IP multicast fast switching is enabled on the outgoing interface on the last hop router.

show ip mfib

Displays the forwarding entries and interfaces in the IP Multicast Forwarding Information Base (MFIB).

show ip pim interface count

Displays statistics related to the number of multicast packets received by and sent out a PIM-enabled interface.

  • Use this command on the last hop router to confirm that multicast traffic is being forwarded on the last hop router.

show ip mroute active

Displays the rate that active sources are sending to multicast groups, in kilobits per second (kb/s).

  • Use this command to display information about the multicast packet rate for active sources sending to groups on the last hop router.

show ip mroute count

Displays statistics related to mroutes in the mroute table.

  • Use this command on the last hop router to confirm that multicast traffic is flowing on the last hop router.

Common Commands Used to Verify IP Multicast Operation on Routers Along the SPT for PIM-SM and PIM-SSM

The table describes the common commands used to verify IP multicast operation on routers along the SPT in PIM-SM and PIM-SSM network environments.

Table 2 Common IP Multicast Verification Commands (Routers Along SPT)

Command

Description and Purpose

show ip mroute

Displays the contents of the mroute table.

  • Use this command to confirm that the Reverse Path Forwarding (RPF) neighbor toward the source is the expected RPF neighbor for each router along the SPT.

show ip mroute active

Displays the rate that active sources are sending to multicast groups, in kb/s.

  • Use this command to display information about the multicast packet rate for active sources sending to groups on routers along the SPT.

Common Commands Used to Verify IP Multicast Operation on the First Hop Router for PIM-SM and PIM-SSM

The table describes the common commands used to verify IP multicast operation on the first hop router in PIM-SM and PIM-SSM network environments.

Table 3 Common IP Multicast Verification Commands (First Hop Router)

Command

Description and Purpose

show ip mroute

Displays the contents of the mroute table.

  • Use this command to confirm that the F flag is set for the mroutes on the first hop router.

show ip mroute active

Displays the rate that active sources are sending to multicast groups, in kb/s.

  • Use this command to display information about the multicast packet rate for active sources sending to groups on the first hop router.

How to Verify IP Multicast Operation

Using PIM-Enabled Routers to Test IP Multicast Reachability

Perform the following tasks to use PIM-enabled routers to test IP multicast reachability.

If all the PIM-enabled routers and access servers that you administer are members of a multicast group, pinging that group causes all routers to respond, which can be a useful administrative and debugging tool.

To use PIM-enabled routers to test IP multicast reachability, perform the following tasks:

Configuring Routers to Respond to Multicast Pings

Perform the following task to configure routers to respond to multicast pings. Performing this task configures interfaces on the router to join a specified group. This task should be performed on each interface on the router participating in the multicast network and on all routers participating in the multicast network.

SUMMARY STEPS

    1.    enable

    2.    configure terminal

    3.    interface type number

    4.    ip igmp join-group group-address

    5.    Repeat Step 3 and Step 4 for each interface on the router participating in the multicast network.

    6.    end


DETAILED STEPS
     Command or ActionPurpose
    Step 1 enable


    Example: 
    Device> enable
     

    Enables privileged EXEC mode. Enter your password if prompted.

     
    Step 2 configure terminal


    Example: 
    Device# configure terminal
     

    Enters global configuration mode.

     
    Step 3 interface type number


    Example: 
    Device(config)# interface gigabitethernet 1/0/0
     

    Enters interface configuration mode.

    For the type and number arguments, specify an interface that is directly connected to hosts or is facing hosts.

     
    Step 4 ip igmp join-group group-address


    Example: 
    Device(config-if)# ip igmp join-group 225.2.2.2
     

    (Optional) Configures an interface on the router to join the specified group.

    For the purpose of this task, configure the same group address for the group-address argument on all interfaces on the router participating in the multicast network.

    Note   

    With this method, the router accepts the multicast packets in addition to forwarding them. Accepting the multicast packets prevents the router from fast switching.

     
    Step 5 Repeat Step 3 and Step 4 for each interface on the router participating in the multicast network.  

    --

     
    Step 6 end


    Example: 
    Device(config-if)# end
     

    Ends the current configuration session and returns to privileged EXEC mode.

     

    Pinging Routers Configured to Respond to Multicast Pings

    Perform the following task on a router to initiate a ping test to the routers configured to respond to multicast pings. This task is used to test IP multicast reachability in a network.

    SUMMARY STEPS

      1.    enable

      2.    ping group-address


    DETAILED STEPS
       Command or ActionPurpose
      Step 1 enable


      Example: 
      Device> enable
       

      Enables privileged EXEC mode. Enter your password if prompted.

       
      Step 2 ping group-address


      Example: 
      Device# ping 225.2.2.2
       

      Pings an IP multicast group address.

      A successful response indicates that the group address is functioning.

       

      Verifying IP Multicast Operation in a PIM-SM or a PIM-SSM Network

      Perform the following optional tasks to verify IP multicast operation in a PIM-SM or a PIM-SSM network. The steps in these tasks help to locate a faulty hop when sources and receivers are not operating as expected.


      Note

      If packets are not reaching their expected destinations, you might want consider disabling IP multicast fast switching, which would place the router in process switching mode. If packets begin reaching their proper destinations after IP multicast fast switching has been disabled, then the issue most likely was related to IP multicast fast switching. See the “ Monitoring and Maintaining IP Multicast ” module for information on how to disable IP multicast fast switching.

      To verify IP multicast operation in a PIM-SM or PIM-SSM multicast network, perform the following verification tasks:

      Verifying IP Multicast Operation on the Last Hop Router

      Perform the following task to verify the operation of IP multicast on the last hop router.


      Note

      If you are verifying a last hop router in a PIM-SSM network, ignore Step 3.

      SUMMARY STEPS

        1.    enable

        2.    show ip igmp groups

        3.    show ip pim rp mapping

        4.    show ip mroute

        5.    show ip interface [type number]

        6.    show ip mfib

        7.    show ip pim interface count

        8.    show ip mroute count

        9.    show ip mroute active [kb/s]


      DETAILED STEPS
        Step 1   enable

        Enables privileged EXEC mode. Enter your password if prompted. 

        Device> enable
        Step 2   show ip igmp groups

        Use this command to verify IGMP memberships on the last hop router. This information will confirm the multicast groups with receivers that are directly connected to the last hop router and that are learned through IGMP.

        The following is sample output from the show ip igmp groups command:



        Example: 
        Router# show ip igmp groups
IGMP Connected Group Membership
Group Address    Interface                Uptime    Expires   Last Reporter
239.1.2.3        GigabitEthernet1/0/0     00:05:14  00:02:14  10.1.0.6
224.0.1.39       GigabitEthernet0/0/0     00:09:11  00:02:08  172.31.100.1
        Step 3   show ip pim rp mapping

        Use this command to confirm that the group-to-RP mappings are being populated correctly on the last hop router.

        Note   

        Ignore this step if you are verifying a last hop router in a PIM-SSM network. The show ip pim rp mappingcommand does not work with routers in a PIM-SSM network because PIM-SSM does not use RPs. In addition, if configured correctly, PIM-SSM groups should not appear in the output of the show ip pim rp mappingcommand.

        The following is sample output from the show ip pim rp mappingcommand:



        Example: 
        Router# show ip pim rp mapping
PIM Group-to-RP Mappings
 
Group(s) 224.0.0.0/4
  RP 172.16.0.1 (?), v2v1 
    Info source: 172.16.0.1 (?), elected via Auto-RP
         Uptime: 00:09:11, expires: 00:02:47
        Step 4   show ip mroute

        Use this command to verify that the mroute table is being populated properly on the last hop router.

        The following is sample output from the show ip mroute command:



        Example: 
        Router# show ip mroute
(*, 239.1.2.3), 00:05:14/00:03:04, RP 172.16.0.1, flags: SJC
  Incoming interface: GigabitEthernet0/0/0, RPF nbr 172.31.100.1
  Outgoing interface list:
  GigabitEthernet1/0, Forward/Sparse-Dense, 00:05:10/00:03:04
 
(10.0.0.1, 239.1.2.3), 00:02:49/00:03:29, flags: T  
  Incoming interface: GigabitEthernet0/0/0, RPF nbr 172.31.100.1  
  Outgoing interface list:
  GigabitEthernet1/0, Forward/Sparse-Dense, 00:02:49/00:03:04
 
(*, 224.0.1.39), 00:10:05/stopped, RP 0.0.0.0, flags: DC
  Incoming interface: Null, RPF nbr 0.0.0.0
  Outgoing interface list:
    GigabitEthernet1/0, Forward/Sparse-Dense, 00:05:15/00:00:00
    GigabitEthernet0/0, Forward/Sparse-Dense, 00:10:05/00:00:00
 
(172.16.0.1, 224.0.1.39), 00:02:00/00:01:33, flags: PTX
  Incoming interface: GigabitEthernet0/0/0, RPF nbr 172.31.100.1
        Step 5   show ip interface [type number]

        Use this command to verify that multicast fast switching is enabled for optimal performance on the outgoing interface on the last hop router.

        Note   

        Using the no ip mroute-cache interface command disables IP multicast fast-switching. When IP multicast fast switching is disabled, packets are forwarded through the process-switched path.

        The following is sample output from the show ip interfacecommand for a particular interface:



        Example: 
        Router# show ip interface GigabitEthernet 0/0/0
GigabitEthernet0/0 is up, line protocol is up
  Internet address is 172.31.100.2/24
  Broadcast address is 255.255.255.255
  Address determined by setup command
  MTU is 1500 bytes
  Helper address is not set
  Directed broadcast forwarding is disabled
  Multicast reserved groups joined: 224.0.0.1 224.0.0.22 224.0.0.13
      224.0.0.5 224.0.0.6
  Outgoing access list is not set
  Inbound  access list is not set
  Proxy ARP is enabled
  Local Proxy ARP is disabled
  Security level is default
  Split horizon is enabled
  ICMP redirects are always sent
  ICMP unreachables are always sent
  ICMP mask replies are never sent
  IP fast switching is enabled
  IP fast switching on the same interface is disabled
  IP Flow switching is disabled
  IP CEF switching is disabled
  IP Fast switching turbo vector
  IP multicast fast switching is enabled
  IP multicast distributed fast switching is disabled
  IP route-cache flags are Fast
  Router Discovery is disabled
  IP output packet accounting is disabled
  IP access violation accounting is disabled
  TCP/IP header compression is disabled
  RTP/IP header compression is disabled
  Policy routing is disabled
  Network address translation is disabled
  WCCP Redirect outbound is disabled
  WCCP Redirect inbound is disabled
  WCCP Redirect exclude is disabled
  BGP Policy Mapping is disabled
        Step 6   show ip mfib

        Use this command to display the forwarding entries and interfaces in the IP Multicast Forwarding Information Base (MFIB).



        Example: 
        
 
			 
        

		  
        

        Step 7  
                 
			  
				show
				
				ip 
				pim 
				interface 
				count 
			  
		  
          
			 
         Use this
				command to confirm that multicast traffic is being forwarded on the last hop
				router.
			 
        
 
			 
         The following
				is sample output from the 
				  show 
				  ip
				  
				  pim 
				  interface command with the 
				count
				keyword:
			 
        
 
		   

        Example:
			 
         
				
        Router# show ip pim interface count
 
State: * - Fast Switched, D - Distributed Fast Switched
       H - Hardware Switching Enabled
Address          Interface                FS Mpackets In/Out
172.31.100.2     GigabitEthernet0/0/0     *   4122/0
10.1.0.1         GigabitEthernet1/0/0     *   0/3193

        
 
			 
        

		  
        

        Step 8  
                 
			  
				show
				
				ip 
				mroute 
				count 
			  
		  
          
			 
         Use this
				command to confirm that multicast traffic is being forwarded on the last hop
				router.
			 
        
 
			 
         The following
				is sample output from the 
				show 
				  ip
				  
				  mroutecommand with the 
				count
				keyword:
			 
        
 
		   

        Example:
			 
         
				
        Router# show ip mroute count
IP Multicast Statistics
6 routes using 4008 bytes of memory
3 groups, 1.00 average sources per group
Forwarding Counts: Pkt Count/Pkts per second/Avg Pkt Size/Kilobits per second
Other counts: Total/RPF failed/Other drops(OIF-null, rate-limit etc)
 
Group: 239.1.2.3, Source count: 1, Packets forwarded: 3165, Packets received: 3165
  RP-tree: Forwarding: 0/0/0/0, Other: 0/0/0
  Source: 10.0.0.1/32, Forwarding: 3165/20/28/4, Other: 0/0/0  
 
Group: 224.0.1.39, Source count: 1, Packets forwarded: 21, Packets received: 120
  Source: 172.16.0.1/32, Forwarding: 21/1/48/0, Other: 120/0/99
 
Group: 224.0.1.40, Source count: 1, Packets forwarded: 10, Packets received: 10
  Source: 172.16.0.1/32, Forwarding: 10/1/48/0, Other: 10/0/0

        
 
			 
        

		  
        

        Step 9  
                 
			  
				show
				
				ip 
				mroute 
				active 
			 [kb/s]
		  
          
			 
         Use this
				command on the last hop router to display information about active multicast
				sources sending traffic to groups on the last hop router. The output of this
				command provides information about the multicast packet rate for active
				sources.
			 
        
 
			 
        Note   
                
              
				
         By default,
				  the output of the 
				  show 
					 ip 
					 mroute command with the 
				  active
				  keyword displays information about active sources sending traffic to groups at
				  a rate greater than or equal to 4 kb/s. To display information about active
				  sources sending low-rate traffic to groups (that is, traffic less than 4 kb/s),
				  specify a value of 1 for the 
				  kb/s
				  argument. Specifying a value of 1 for this argument displays information about
				  active sources sending traffic to groups at a rate equal to or greater than 1
				  kb/s, which effectively displays information about all possible active source
				  traffic.
				
        

			 
        
 
			 
         The following
				is sample output from the 
				show 
				  ip
				  
				  mroutecommand with the 
				active
				keyword:
			 
        
 
		   

        Example:
			 
         
				
        Router# show ip mroute active
Active IP Multicast Sources - sending >= 4 kbps
 
Group: 239.1.2.3, (?)
   Source: 10.0.0.1 (?)
     Rate: 20 pps/4 kbps(1sec), 4 kbps(last 50 secs), 4 kbps(life avg) 
        
 
			 
        

		  
        

        

        

        

        Verifying IP Multicast on Routers Along the SPT
        

        
      
        
Perform the following task to verify the operation of IP multicast on routers along the SPT in a PIM-SM or PIM-SSM network.
        

    
        
SUMMARY STEPS
          1.   
      
          
            enable
          
        
          

          2.   
      
          
            show
            ip
            mroute
           [group-address]
          

          3.   
      
          
            show
            ip
            mroute
            active
          
        
          


        DETAILED STEPS
          Step 1  
                
          
            enable
          
        
           
          
          
Enables privileged EXEC mode. Enter your password if prompted.
          

          
          Router> enable
          

          
          

        
          

          Step 2  
                
          
            show
            ip
            mroute
           [group-address]
           
          
          
Use this command on routers along the SPT to confirm the RPF neighbor toward the source for a particular group or groups.
          

          
          
The following is sample output from the show ip mroutecommand for a particular group:
          

         

          Example:
          
          
          Router# show ip mroute 239.1.2.3
(*, 239.1.2.3), 00:17:56/00:03:02, RP 172.16.0.1, flags: S
  Incoming interface: Null, RPF nbr 0.0.0.0
  Outgoing interface list:
    GigabitEthernet0/0/0, Forward/Sparse-Dense, 00:17:56/00:03:02
 
(10.0.0.1, 239.1.2.3), 00:15:34/00:03:28, flags: T
  Incoming interface: Serial1/0, RPF nbr 172.31.200.1  
  Outgoing interface list:
    GigabitEthernet0/0/0, Forward/Sparse-Dense, 00:15:34/00:03:02

          

        
          

          

          Step 3  
                
          
            show
            ip
            mroute
            active
          
        
           
          
          
Use this command on routers along the SPT to display information about active multicast sources sending to groups. The output of this command provides information about the multicast packet rate for active sources.
          

          
          Note   
                
              
          
By default, the output of the show ip mroute command with the active keyword displays information about active sources sending traffic to groups at a rate greater than or equal to 4 kb/s. To display information about active sources sending low-rate traffic to groups (that is, traffic less than 4 kb/s), specify a value of 1 for the kb/s argument. Specifying a value of 1 for this argument displays information about active sources sending traffic to groups at a rate equal to or greater than 1 kb/s, which effectively displays information about all possible active source traffic.
          

          

          
          
The following is sample output from the show ip mroute command with the active keyword:
          

         

          Example:
          
          
          Router# show ip mroute active
Active IP Multicast Sources - sending >= 4 kbps
 
Group: 239.1.2.3, (?)
   Source: 10.0.0.1 (?)
     Rate: 20 pps/4 kbps(1sec), 4 kbps(last 30 secs), 4 kbps(life avg) 
          

        
          

          

          

          

          

          Verifying IP Multicast on the First Hop Router
          

          
      
          
Perform the following task to verify the operation of IP multicast on the first hop router.
          

    
          
SUMMARY STEPS
            1.   
      
          
            enable
          
        
            

            2.   
      
          
            show
            ip
            mroute
           [group-address]
            

            3.   
      
          
            show
            ip
            mroute
            active
          [kb/s]
            


          DETAILED STEPS
            Step 1  
                
          
            enable
          
        
             
          
            
Enables privileged EXEC mode. 
            

          
            • 
Enter your password if prompted.
              

              • 

            

          
            
            
            
          
            

          
            Router> enable
            

          
            

        
            

            Step 2  
                
          
            show
            ip
            mroute
           [group-address]
             
          
            
Use this command on the first hop router to confirm the F flag has been set for mroutes on the first hop router. 
            

          
            
The following is sample output from the show ip mroutefor a particular group:
            

         

            Example:
            
          
            Router# show ip mroute 239.1.2.3
(*, 239.1.2.3), 00:18:10/stopped, RP 172.16.0.1, flags: SPF
  Incoming interface: Serial1/0, RPF nbr 172.31.200.2
  Outgoing interface list: Null
 
(10.0.0.1, 239.1.2.3), 00:18:10/00:03:22, flags: FT
  Incoming interface: GigabitEthernet0/0/0, RPF nbr 0.0.0.0  
  Outgoing interface list:
    Serial1/0, Forward/Sparse-Dense, 00:18:10/00:03:19

            

        
            

            

            Step 3  
                
          
            show
            ip
            mroute
            active
          [kb/s]
             
          
            
Use this command on the first hop router to display information about active multicast sources sending to groups. The output of this command provides information about the multicast packet rate for active sources.
            

          
            Note   
                
              
            
By default, the output of the show ip mroute command with the active keyword displays information about active sources sending traffic to groups at a rate greater than or equal to 4 kb/s. To display information about active sources sending low-rate traffic to groups (that is, traffic less than 4 kb/s), specify a value of 1 for the kb/s argument. Specifying a value of 1 for this argument displays information about active sources sending traffic to groups at a rate equal to or greater than 1 kb/s, which effectively displays information about all possible active source traffic.
            

            

          
            
The following is sample output from the show ip mroute command with the active keyword:
            

         

            Example:
            
          
            Router# show ip mroute active
Active IP Multicast Sources - sending >= 4 kbps
 
Group: 239.1.2.3, (?)
   Source: 10.0.0.1 (?)
     Rate: 20 pps/4 kbps(1sec), 4 kbps(last 30 secs), 4 kbps(life avg) 
            

        
            

            

            

            

            

            

            

            Configuration Examples for Verifying IP Multicast Operation
            

            
    
            

            

            Verifying IP Multicast Operation in a PIM-SM or PIM-SSM Network Example
            

             
		
             The following example shows how to verify IP multicast operation after PIM-SM has been deployed in a network. The example is based on the PIM-SM topology illustrated in the figure. 
		
            
 
		
             From the last hop router to the first hop router shown in the figure, this example shows how to verify IP multicast operation for this particular PIM-SM network topology. 
		
            
 
		


            
 
	 
            

            

            Verifying IP Multicast on the Last Hop Router Example
            

             
		
             The following is sample output from the 
		  show 
			 ip 
			 igmp 
			 groups command. The sample output displays the IGMP memberships on the last hop router shown in the figure. This command is used in this example to confirm that the IGMP cache is being properly populated for the groups that receivers on the LAN have joined.
		
            
 
		
            Router# show ip igmp groups
IGMP Connected Group Membership
Group Address    Interface                Uptime    Expires   Last Reporter
239.1.2.3        GigabitEthernet1/0/0     00:05:14  00:02:14  10.1.0.6
224.0.1.39       GigabitEthernet0/0/0     00:09:11  00:02:08  172.31.100.1

            
 
		
             The following is sample output from the 
		  show 
			 ip 
			 pim 
			 rp 
			 mappingcommand. In the sample output, notice the RP address displayed for the RP field. Use the RP address and group information to verify that the group-to-RP mappings have been properly populated on the last hop router shown in the figure.
		
            
 
		

            Note
             In the output, the “(?)” indicates that the router is unable to resolve an IP address to a hostname.
		
            

            
 
		
            Router# show ip pim rp mapping
PIM Group-to-RP Mappings
 
Group(s) 224.0.0.0/4
  RP 172.16.0.1 (?), v2v1 
    Info source: 172.16.0.1 (?), elected via Auto-RP
         Uptime: 00:09:11, expires: 00:02:47

            
 
		
             The following is sample output from the 
			 show 
			 ip 
			 mroute command. This command is used to verify that the mroute table is being properly populated on the last hop router shown in the figure. In the sample output, notice the T flag for the (10.0.0.1, 239.1.2.3) mroute. The T flag indicates that the SPT-bit has been set, which means a multicast packet was received on the SPT tree for this particular mroute. In addition, the RPF nbr field should point toward the RPF neighbor with the highest IP address determined by unicast routing toward the multicast source.
		
            
 
		
            Router# show ip mroute
(*, 239.1.2.3), 00:05:14/00:03:04, RP 172.16.0.1, flags: SJC
  Incoming interface: GigabitEthernet0/0/0, RPF nbr 172.31.100.1
  Outgoing interface list:
    Ethernet1/0, Forward/Sparse-Dense, 00:05:10/00:03:04
 
(10.0.0.1, 239.1.2.3), 00:02:49/00:03:29, flags: T  
  Incoming interface: GigabitEthernet0/0/0, RPF nbr 172.31.100.1  
  Outgoing interface list:
    Ethernet1/0, Forward/Sparse-Dense, 00:02:49/00:03:04
 
(*, 224.0.1.39), 00:10:05/stopped, RP 0.0.0.0, flags: DC
  Incoming interface: Null, RPF nbr 0.0.0.0
  Outgoing interface list:
    Ethernet1/0, Forward/Sparse-Dense, 00:05:15/00:00:00
    Ethernet0/0, Forward/Sparse-Dense, 00:10:05/00:00:00

            
 
		
             The following is sample output from the 
		  show 
			 ip 
			 interface command for the incoming interface. This command is used in this example to confirm that IP multicast fast switching is enabled on the last hop router shown in the figure. When IP multicast fast switching is enabled, the line “IP multicast fast switching is enabled” displays in the output.
		
            
 
		
            Router# show ip interface GigabitEthernet 0/0/0
GigabitEthernet0/0/0 is up, line protocol is up
  Internet address is 172.31.100.2/24
  Broadcast address is 255.255.255.255
  Address determined by setup command
  MTU is 1500 bytes
  Helper address is not set
  Directed broadcast forwarding is disabled
  Multicast reserved groups joined: 224.0.0.1 224.0.0.22 224.0.0.13
      224.0.0.5 224.0.0.6
  Outgoing access list is not set
  Inbound  access list is not set
  Proxy ARP is enabled
  Local Proxy ARP is disabled
  Security level is default
  Split horizon is enabled
  ICMP redirects are always sent
  ICMP unreachables are always sent
  ICMP mask replies are never sent
  IP fast switching is enabled
  IP fast switching on the same interface is disabled
  IP Flow switching is disabled
  IP CEF switching is disabled
  IP Fast switching turbo vector
  IP multicast fast switching is enabled
  IP multicast distributed fast switching is disabled
  IP route-cache flags are Fast
  Router Discovery is disabled
  IP output packet accounting is disabled
  IP access violation accounting is disabled
  TCP/IP header compression is disabled
  RTP/IP header compression is disabled
  Policy routing is disabled
  Network address translation is disabled
  WCCP Redirect outbound is disabled
  WCCP Redirect inbound is disabled
  WCCP Redirect exclude is disabled
  BGP Policy Mapping is disabled

            
 
		
             The following is sample output from the 
			 show 
			 ip 
			 pim 
			 interface 
		  count command. This command is used in this example to confirm that multicast traffic is being forwarded to the last hop router shown in the figure. In the sample output, notice the Mpackets In/Out field. This field displays the number of multicast packets received by and sent on each interface listed in the output.
		
            
 
		
            Router# show ip pim interface count
 
State: * - Fast Switched, D - Distributed Fast Switched
       H - Hardware Switching Enabled
Address          Interface                FS Mpackets In/Out
172.31.100.2     GigabitEthernet0/0/0     *   4122/0
10.1.0.1         GigabitEthernet1/0/0     *   0/3193

            
 
		
             The following is sample output from the 
		  show 
			 ip 
			 mroutecommand with the 
		  count keyword. This command is used on the last hop router shown in the figure to verify the packets being sent to groups from active sources. In the sample output, notice the packet count displayed for the Forwarding field. This field displays the packet forwarding count for sources sending to groups.
		
            
 
		
            Router# show ip mroute count
IP Multicast Statistics
6 routes using 4008 bytes of memory
3 groups, 1.00 average sources per group
Forwarding Counts: Pkt Count/Pkts per second/Avg Pkt Size/Kilobits per second
Other counts: Total/RPF failed/Other drops(OIF-null, rate-limit etc)
 
Group: 239.1.2.3, Source count: 1, Packets forwarded: 3165, Packets received: 3165
  RP-tree: Forwarding: 0/0/0/0, Other: 0/0/0
  Source: 10.0.0.1/32, Forwarding: 3165/20/28/4, Other: 0/0/0  
 
Group: 224.0.1.39, Source count: 1, Packets forwarded: 21, Packets received: 120
  Source: 172.16.0.1/32, Forwarding: 21/1/48/0, Other: 120/0/99
 
Group: 224.0.1.40, Source count: 1, Packets forwarded: 10, Packets received: 10
  Source: 172.16.0.1/32, Forwarding: 10/1/48/0, Other: 10/0/0

            
 
		
             The following is sample output from the 
		  show 
			 ip 
			 mroutecommand with the 
		  active keyword. This command is used on the last hop router shown in the figure to confirm the multicast groups with active sources on the last hop router.
		
            
 
		

            Note
             In the output, the “(?)” indicates that the router is unable to resolve an IP address to a hostname.
		
            

            
 
		
            Router# show ip mroute active
Active IP Multicast Sources - sending >= 4 kbps
 
Group: 239.1.2.3, (?)
   Source: 10.0.0.1 (?)
     Rate: 20 pps/4 kbps(1sec), 4 kbps(last 50 secs), 4 kbps(life avg) 
            
 
	 
            

            

            

            Verifying IP Multicast on Routers Along the SPT Example
            

             
		
             The following is sample output from the 
		  show 
			 ip 
			 mroutefor a particular group. This command is used in this example to verify that the RPF neighbor toward the source is the expected RPF neighbor for the router along the SPT shown in the figure.
		
            
 
		
            Router# show ip mroute 239.1.2.3
(*, 239.1.2.3), 00:17:56/00:03:02, RP 172.16.0.1, flags: S
  Incoming interface: Null, RPF nbr 0.0.0.0
  Outgoing interface list:
    Ethernet0/0, Forward/Sparse-Dense, 00:17:56/00:03:02
 
(10.0.0.1, 239.1.2.3), 00:15:34/00:03:28, flags: T
  Incoming interface: Serial1/0, RPF nbr 172.31.200.1  
  Outgoing interface list:
            
 
		
             Ethernet0/0, Forward/Sparse-Dense, 00:15:34/00:03:02
		
            
 
		
             The following is sample output from the 
			 show 
			 ip 
			 mroute command with the 
		  active keyword from the router along the SPT shown in the figure. This command is used to confirm the multicast groups with active sources on this router.
		
            
 
		

            Note
             In the output, the “(?)” indicates that the router is unable to resolve an IP address to a hostname.
		
            

            
 
		
            Router# show ip mroute active
Active IP Multicast Sources - sending >= 4 kbps
 
Group: 239.1.2.3, (?)
   Source: 10.0.0.1 (?)
     Rate: 20 pps/4 kbps(1sec), 4 kbps(last 30 secs), 4 kbps(life avg) 
            
 
	 
            

            

            

            Verifying IP Multicast on the First Hop Router Example
            

             
		
             The following is sample output from the 
		  show 
			 ip 
			 mroutefor a particular group. This command is used in this example to verify the packets being sent to groups from active sources on the first hop router shown in the figure. In the sample output, notice the packet count displayed for the Forwarding field. This field displays the packet forwarding count for sources sending to groups on the first hop router.
		
            
 
		

            Note
             The RPF nbr 0.0.0.0 field indicates that the source of an mroute has been reached.
		
            

            
 
		
            Router# show ip mroute 239.1.2.3
(*, 239.1.2.3), 00:18:10/stopped, RP 172.16.0.1, flags: SPF
  Incoming interface: Serial1/0, RPF nbr 172.31.200.2
  Outgoing interface list: Null
 
(10.0.0.1, 239.1.2.3), 00:18:10/00:03:22, flags: FT
  Incoming interface: GigabitEthernet0/0/0, RPF nbr 0.0.0.0  
  Outgoing interface list:
    Serial1/0/0, Forward/Sparse-Dense, 00:18:10/00:03:19

            
 
		
             The following is sample output from the 
			 show 
			 ip 
			 mroute command with the 
		  active keyword from the first hop router shown in the figure:
		
            
 
		

            Note
             In the output, the “(?)” indicates that the router is unable to resolve an IP address to a host name.
		
            

            
 
		
            Router# show ip mroute active
Active IP Multicast Sources - sending >= 4 kbps
 
Group: 239.1.2.3, (?)
   Source: 10.0.0.1 (?)
     Rate: 20 pps/4 kbps(1sec), 4 kbps(last 30 secs), 4 kbps(life avg) 
            
 
	 
            

            

            

            

            

            Additional References
            

             
	 
            

            Related Documents
             
		 
		

             
					 
             Related Topic
					 
            
 
				              		
 
					 
             Document Title
					 
            
 
				              		

            
            

             
					 
             Overview of the IP multicast technology area 
					 
            
 
				              		
 
					 
             “ IP Multicast Technology Overview ” module
					 
            
 
				              		

            

             
					 
             PIM-SM and SSM concepts and configuration examples 
					 
            
 
				              		
 
					 
             “ Configuring Basic IP Multicast ” module
					 
            
 
				              		

            

             
					 
             IP multicast commands: complete command syntax, command mode, command history, defaults, usage guidelines, and examples 
					 
            
 
				              		
 
					 
             
						Cisco IOS IP Multicast Command Reference 
					 
            
 
				              		

            
            

            

            
 
	 
            

            Standards
             
		 
		

             
					 
             Standard
					 
            
 
				              		
 
					 
             Title
					 
            
 
				              		

            
            

             
					 
             No new or modified standards are supported, and support for existing standards has not been modified. 
					 
            
 
				              		
 
					 
             --
					 
            
 
				              		

            
            

            

            
 
	 
            

            MIBs
             
		 
		

             
					 
             MIB
					 
            
 
				              		
 
					 
             MIBs Link
					 
            
 
				              		

            
            

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

             
					 
             RFC
					 
            
 
				              		
 
					 
             Title
					 
            
 
				              		

            
            

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

            
            

            

            
 
	 
            

            Technical Assistance
             
		 
		

             
					 
             Description
					 
            
 
				              		
 
					 
             Link
					 
            
 
				              		

            
            

             
					 
             The Cisco Support website provides extensive online resources, including documentation and tools for troubleshooting and resolving technical issues with Cisco products and technologies.
					 
            
 
					 
             To receive security and technical information about your products, you can subscribe to various services, such as the Product Alert Tool (accessed from Field Notices), the Cisco Technical Services Newsletter, and Really Simple Syndication (RSS) Feeds.
					 
            
 
					 
             Access to most tools on the Cisco Support website requires a Cisco.com user ID and password.
					 
            
 
				              		
 
					 
             
						http:/​/​www.cisco.com/​techsupport 
						 
					 
            
 
				              		

            
            

            

            
 
	 
            

            

            

            Feature Information for Verifying IP Multicast Operation
            

            
			
            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 4 Feature Information for Verifying IP Multicast Operation 
             
				  
             Feature Name
				  
            
 
				            		
 
				  
             Releases
				  
            
 
				            		
 
				  
             Feature Information
				  
            
 
				            		

            
            

             
				  
             This table is intentionally left blank because no features were introduced or modified in this module since Cisco IOS XE Release 2(1). This table will be updated when feature information is added to this module. 
				  
            
 
				            		
 
				  
             --
				  
            
 
				            		
 
				  
             --