RE: PIM Sparse-Dense / Auto-RP

From: Hogo, Trust (trust.hogo@sarcom.com)
Date: Sun Feb 29 2004 - 02:26:15 GMT-3

 In sparse-mode the routers need to know the rp-addresses, this is
accomplished by statically defining rp-address or by enabling
sparse-dense-mode. In this mode the router uses the dense-mode to learn
who the rps are, infect it uses groups 224.0.1.39 and 224.0.1.40 to
learn about Auto-rps. Once it knows the rps it will then use sparse mode
for all the groups defined by the those rps and any groups not defined
it will use dense mode. Infect now to use auto-rp you no longer need to
specify sparse-dense mode, you simply use sparse-mode and the command
"ip pim autorp listener" this will use the above mentioned groups to
learn auto-rps and accomplish the same.

Hope this helps.
Trust

-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
ihatecisco@att.net
Sent: Saturday, February 28, 2004 9:34 PM
To: ccielab@groupstudy.com
Subject: PIM Sparse-Dense / Auto-RP

I am just wanting to go over my understanding of Auto-RP, specifically
how it relates to ip pim sparse-dense-mode

When you configure auto-rp. You setup the RP/Mapping agent as

ip multicast-routing
ip pim send-rp-annouce loopback0 scope 255 (no group list)
ip pim send-rp-discovery scope 128

interface lo0
ip address 10.1.1.1 255.255.255.0
ip pim sparse-dense-mode

interface eth0
ip address 192.168.1.1 255.255.255.0
ip pim sparse-dense-mode

-----------------------------------

So in this instance we are sending out the PIM Auto-RP advertisement for
the entire multicast address range.

224.0.0.0/4

128 * 64 * 32 * 16 * 8 * 4 * 2 * 1
------------------------------------------------------------------------
----- 

--
 1             1          1          0    |   0       0       0       0

This covers the entire multicast range.

According to the cisco configuration documentation. [very limited and
obscure might i add]  It states that sparse-dense mode will operate as
sparse mode for multicast groups that have RP's defined, and sparse mode
for groups that do not have RPs defined.

Do you have to specificially configure the ip send-rp-announce command
with an access list, or is using the default behavior, [all multicast
groups] still "play nice" with sparse-dense mode?

Any questions or comments welcome.

**Reading the FM**

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