multicast sparse mode

CCIE_2011

Hi all....
I'm trying to finish my multicast lab here....

when i ping a group from multiple sources. The multicast routing table creates a multicast routing entry for each source....

Should all the sources use the general multicast routing entry (*, G) ???? to save routing resources and memory!!!! correct? ?

This is suppose to be the difference between Sparse and dense as per my understanding

thanks

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Comments

kryolla

with sparse mode you have 2 types of trees, a share tree or RPT which is *,G and is built from the receiver DR to RP and you have a source tree S,G that is built from the source DR to RP. The RP will send a S,G entry to the receiver DR and then it switches to source tree or SPT. A *,G entry is created because the receiver DR doesn't know the source and the only router that knows that source is the RP so when a receiver send an IGMP join to the DR of the segment it is JUST for the group. Then the DR will send PIM join *,G upstream until it reaches the RP.

jason_lunde

Great explanation Kryolla! Multicast and BGP were the hardest things for me to grasp when I was studying for my BSCI. I had to hit them pretty hard, both reading and labbing.

CCIE_2011

thanks for that dude. .....

I really liked your explanations and style .... You should really think of writing a book

regarding my question
So the main difference between sparse and dense modes is how each start in building the tree.
sparse and dense trees are alike once the trees are built.

I really appreciate your help

kryolla

CCIE_2011 wrote: »

thanks for that dude. .....

I really liked your explanations and style .... You should really think of writing a book

regarding my question
So the main difference between sparse and dense modes is how each start in building the tree.
sparse and dense trees are alike once the trees are built.

I really appreciate your help

yes dense only has S,G since the source DR just floods it out all PIM enabled interfaces and it travels downstream until it reaches the receiver. Then each router just prunes it back if doesnt have anybody that wants it.