# Confusing about auto-RP

**URL:** <https://forum.networklessons.com/t/confusing-about-auto-rp/4093>\
**Category:** Multicast\
**Created:** [June 15, 2018, 6:38pm UTC](https://forum.networklessons.com/t/confusing-about-auto-rp/4093 "2018-06-15T18:38:02Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![telecosistem](https://cdn-forum.networklessons.com/user_avatar/forum.networklessons.com/telecosistem/32/854_2.png) [@telecosistem](https://forum.networklessons.com/u/telecosistem)\
**Post date:** [June 15, 2018, 6:38pm UTC](https://forum.networklessons.com/t/confusing-about-auto-rp/4093/1 "2018-06-15T18:38:02Z")

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Hey mates,  
I am having doubts about using auto-RP. I know that is necessary to enable dense-mode to announce “224.0.0.39”. But I would like this:  
All interfaces must be configured in sparse-dense mode?  
Can I use loopback interface to tierbreak?  
Thanks in advance!

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**Author:** ![lagapidis](https://cdn-forum.networklessons.com/user_avatar/forum.networklessons.com/lagapidis/32/4949_2.png) [@lagapidis](https://forum.networklessons.com/u/lagapidis)\
**Post date:** [June 19, 2018, 2:24pm UTC](https://forum.networklessons.com/t/confusing-about-auto-rp/4093/2 "2018-06-19T14:24:23Z")

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Hello Alfredo

Take a look at Rene’s lesson on auto-RP here:

> **[Multicast PIM Auto RP](https://networklessons.com/multicast/multicast-ip-pim-auto-rp)**
>
> Multicast PIM Auto RP allows us to automatically discover and advertise an RP (Rendezvous Point) for PIM Sparse mode networks.

Once you go over that, if you have any specific questions, just let us know.

I hope this has been helpful!

Laz