ip pim sparse mode not working anymore but sparse-dense does

[Aaron Greene]

I have a very flat network.  All of the gateways/SVI's exist on the same 6500.  There are some vBrick IPTV servers that have a unicast address and 2-3 multicast addresses configured. After rebooting the 6500, the ip pim sparse-mode we had on all of our SVI's no longer work.  I checked the old config and everything is the same as before I rebooted it.  I troubleshot this for a while and found that the only way I can make this work now is if I enable ip sparse-dense on the SVI's.  I believe this means that dense is the multicast method being used and I don't want to use dense mode because of all the flooding.  How might I be able to make ip pim sparse-mode work again?  I never had a static RP configured but I think I will need to.  How do I decide on what ip address on the 6500 I should use as the RP?  Should the ip address of the RP be a loopback address on the 6500 or should it be the SVI gateway ip of the vlan that the vBrick IPTV servers are on?

[Reza Sharifi]

You don't need to use the SVI or loopback IP address.  You can use another address you want. If your loopback address is

10.10.10.1 you can use 10.10.10.100 for your RP address.  Also, since you have only one router running multicast in your LAN, sparse-dense mode should be fine.

HTH