Understanding RPF Failure

Hi Experts,

Theoritically I understand RPF failure but would like to understand RPF failure w.r.t. output of "sh ip mroute count" as shown below:

RPF Failure:

R1(config-if)#do sh ip mroute coun

Group: 224.0.1.39, Source count: 1, Packets forwarded: 3, Packets received: 7
  Source: 150.1.5.5/32, Forwarding: 3/0/48/0, Other: 7/2/2

Group: 224.0.1.40, Source count: 1, Packets forwarded: 0, Packets received: 13
  Source: 150.1.3.3/32, Forwarding: 0/0/0/0, Other: 14/14/0

 

No RPF Failure:

R1(config)#do sh ip mroute count

Group: 224.0.1.40, Source count: 1, Packets forwarded: 0, Packets received: 13
  Source: 150.1.3.3/32, Forwarding: 1/0/48/0, Other: 14/13/0

I believe understanding "Forwarding" and "Other" output will help us understand RPF failure.

Thanks,

Aashish

 

 

Comments

  • Hi Ashse,

    “show ip mroute count” will show all currently active multicast feeds, and whether packets are getting dropped" and take a look to the following blog entry:

    http://blog.ine.com/2008/01/02/troubleshooting-multicast-rpf-failure/

    And

    http://www.cisco.com/en/US/tech/tk828/technologies_tech_note09186a0080093f21.shtml#showipmroutecount

    Hi Experts,

    Theoritically I understand RPF failure but would like to understand RPF failure w.r.t. output of "sh ip mroute count" as shown below:

    RPF Failure:

    R1(config-if)#do sh ip mroute coun

    Group: 224.0.1.39, Source count: 1, Packets forwarded: 3, Packets received: 7
      Source: 150.1.5.5/32, Forwarding: 3/0/48/0, Other: 7/2/2

    Group: 224.0.1.40, Source count: 1, Packets forwarded: 0, Packets received: 13
      Source: 150.1.3.3/32, Forwarding: 0/0/0/0, Other: 14/14/0

     

    No RPF Failure:

    R1(config)#do sh ip mroute count

    Group: 224.0.1.40, Source count: 1, Packets forwarded: 0, Packets received: 13
      Source: 150.1.3.3/32, Forwarding: 1/0/48/0, Other: 14/13/0

    I believe understanding "Forwarding" and "Other" output will help us understand RPF failure.

    Thanks,

    Aashish

     

     

     

  • Hi Aashish,

    The second decimal after "Other: " is actually the counter for RPF failure. See the decimal circled in below picture. That is the RPF failure counter.
    image

    Your first output shows no multicast packet has been forwarded by the router, total packets = total RPF failed, which is 14.
    While the second output shows one multicast packet has been forwarded and it still shows the total count of RPF failed packets which is 13.

    Please CMIIW.
    Thanks.

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