Auto-RP does it require Sparse-dense mode??

[sandjose]

I was just talking to a freind who worked on a Juniper product .Does the auto-RP in multicast requires the Pim mode to be in sparse-dense mode ??

Can we not work with auto-rp just by enabling the Pim -sparse mode itself .I got a Bit confused when my friend told me that juniper requires sparse-dense mode for auto-rp to work .

Could someone reply ,Thanks in advance

-Sandeep

[oettls]

Sandeep,

this is somewhat a hen / egg problem.

Auto-RP uses 2 multicast groups to distribute infos about RPs:

224.0.1.39 (CISCO-RP-ANNOUNCE ): candidate RPs adv their willingsness to be RP

224.0.1.40 (CISCO-RP-DISCOVERY):

RP mapping agents advertise decisions about RP mappings to other PIM routers

The two groups used for Auto-RP are usually operated in dense mode since you don't know you the RP is at the time ... So you need sparse-dense for Auto-RP (or configure static RPs only for the two groups). As an alternative you can use bootstrap router (or some other mechanism) to distribute RP information, the you could switch to sparse only.

cheers,

Stefan

[Harold Ritter]

You generally have to use sparse-dense mode if you configure auto-rp. Dense mode is used to propagate the announce (224.0.1.39) and discovery (224.0.1.40) messages to all routers in the network.

I said generally because there is a feature, called auto-rp listener that allows you to configure auto-rp in sparse only mode.

Please refer to the following URL for more information on this feature:

http://www.cisco.com/en/US/products/sw/iosswrel/ps5187/products_command_reference_chapter09186a008017cf24.html#wp1068637

Hope this helps,