2 Replies Latest reply: Feb 23, 2011 5:38 PM by jneiberger RSS

    Why does PIM enable IGMP?

    jneiberger

      IGMP is enabled automatically when you enable PIM on an interface and

      I can't figure out why. I've talked to a few other engineers and no

      one can thing of why IGMP would need to be enabled on a

      router-to-router connection running PIM. My only thought was that it

      was a leftover from PIMv1, which used IGMP type 14 packets, but that's

      a total guess.

       

      Do any of you happen to know the answer to this piece of trivia?

       

      Thanks!

      John

        • 1. Re: Why does PIM enable IGMP?
          abdel_n

          Hello jneiberger,


          In addition to the main role of IGMP, managing multicast hosts membership in LAN, it is also used by mtrace command for path checking :

           

          http://tools.ietf.org/html/draft-ietf-magma-igmp-iana-01#section-7

          Type      Name                                    Reference

          ----      ----------------------                  ---------

          0x11      IGMP Membership Query                   [RFC1112]

          0x12      IGMPv1 Membership Report                [RFC1112]

          0x13      DVMRP                                   [RFCDVMRP]

          0x14      PIM version 1                           [PIMv1]

          0x15      Cisco Trace Messages

          0x16      IGMPv2 Membership Report                [RFC2236]

          0x17      IGMPv2 Leave Group                      [RFC2236]

          0x1e      Multicast Traceroute Response           [Fenner]

          0x1f      Multicast Traceroute                    [Fenner]

          0x22      IGMPv3 Membership Report                [RFCIGMPv3]

          0xf0-0xff Reserved for experimentation            [RFCIGMPIANA]

          From the previous post about mtrace :

          igmp-1e.jpg

          igmp-1f.jpg

          • 2. Re: Why does PIM enable IGMP?
            jneiberger

            Oh, we were just talking about that in the other thread!  lol   I should have realized that. Now I feel silly that we had a whole thread about mtrace and it didn't even enter my mind with regard to this question. Thanks!