Multicast Question

ITtech2010ITtech2010 Member Posts: 92 ■■■□□□□□□□
Hi all,

I have a question on Multicast. My environment is using Dense mode to receive multicast traffic. We have for example a A-Feed (binary data) source coming from Carlstadt and a B-Feed (ascii data) coming from Philly. I think eventually my company wants to go into Sparse Mode.

I know with Dense mode the traffic floods to all of our customers that want to receive the data. My question is how would this work with Sparse Mode?

Would I have to configure a router (or 2) as a RP and configure it to allow the A+B feed to distribute the data to our customers?

I guess the part I am stuck at is how would I configure a router to receive data from both A+B feed customers to distribute the data.

Thanks for your help.


  • SubnetZeroSubnetZero Member Posts: 124
    In Sparse mode there are 3 methods of specifying the RP

    - Static Assignment
    - Auto-RP (Cisco Proprietary)
    - Bootstrap Router (BSR - IETF standard)

    Configuration for these methods are as follows (with static being the easiest if there aren't many PIM enabled routers)

    Static RP - Choose your RP and configure it on all of your multicast enabled routers

    ip pim rp-address (acl)

    Auto-RP - Auto-RP is a very old protocol originally designed for dense-mode operations!! If you want to run auto-rp you need to run in ether dense-mode or sparse-dense-mode. There actually is a way to get it to work in sparse mode however this protocol was designed for dense mode!

    Note: Although I don't recommend it you can use it in PIM-SM networks but enabling the "ip pim autorp listener" command on all of your PIM enabled routers

    On the router to be the RP

    ip pim send-rp-announce (src-intf) scope (ttl) group-list (acl)

    On the router to be the Mapping Agent (MA)

    ip pim send-rp-discovery scope (ttl)

    the MA is needed somewhere on the network and can be on the same router as your RP commands, doesn't matter.

    BSR - IETF (open standard) which is their way of dynamically learning RP information

    RP candidates are configured

    ip pim rp-candidate (intf) (ttl)(pri) [group-list]

    The PRI is for priority. Highest priority wins. If tied highest IP address

    BSR config

    ip pim bsr-candidate (intf) (hash) (pri)

    Don't forget to go around to all your PIM enabled interfaces and switch them from dense-mode to sparse-mode (or sparse-dense-mode) and test it this in a lab environment before rolling it out into production!

    While no trees were harmed in the transmission of this message, several electrons were severely inconvenienced
  • SubnetZeroSubnetZero Member Posts: 124
    I would also highly recommend you consult the IP Multicast configuration guide from Cisco

    This documentation has been moved - Configuring Basic IP Multicast  [Support] - Cisco Systems

    I also highly recommend you consider reading the Routing TCP/IP Volume 2 (Doyle)

    This book is a great reference for IP Multicast!


    While no trees were harmed in the transmission of this message, several electrons were severely inconvenienced
  • ITtech2010ITtech2010 Member Posts: 92 ■■■□□□□□□□
    Thanks for your input Subzero! I appreciate you taking the time to explain it. I have the multicast book from Beau Williamson from 1999. People say it's still a great reference so i'll look into that and the tcp ip book you recommended.:)

    Now that I have an understanding of how sparse mode will work i'll on a lab to see how it would come across. My co-workers are purchasing a powerful server so we can run gns3 on it. This will be perfect to implement in the lab.
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