From: Gupta, Gopal (NWCC) (gopal.gupta@hp.com)
Date: Tue Dec 04 2007 - 10:18:14 ART
One Simple thing to remember is that we need pim AutoRP listener on the
Router who needs to send these mappings info to its other neighbors;
otherwise not needed
Even i have a query related to this i have just posted, any comments on
that ???
HTH
Gops
________________________________
From: nhatphuc [mailto:nhatphuc@gmail.com]
Sent: Tuesday, December 04, 2007 18:18
To: Salau, Yemi
Cc: Gupta, Gopal (NWCC); Cisco certification
Subject: Re: IP PIM AutoRP Listener placement?
Hi all,
I've received 3 answers, two of which agree with me, the other doesn't.
Per my testing, R3 and R5 can still receive RP mapping info without
autorp listener command. But in the IEWB 4 lab4, there is a scenario in
which they configure listener command on R3 and R5.
I don't know if it is a must or they just add the command for sure as
Shiran Quez said.
To Salau Yemi: Have you done lab 4 IEWB4 or tested this command on
devices?
To Shiran Quez, Gupta Gopal: What do you think about Salau Yemi's
answer?
Thank you for your replies
Phuc
On Dec 4, 2007 5:05 PM, Salau, Yemi < yemi.salau@siemens.com> wrote:
Basically, ip pim autorp listener is basically telling the
router to
flood multicast traffic for 2 auto-rp groups 224.0.1.39 and
224.0.1.40
across interfaces operating in PIM sparse mode. I believe you
know cRPs
uses 224.0.1.39 to announce/advertise themselves to the MA, and
in turn
the MA routers receive these multicasts, and periodically
advertises
this information to multicast group 224.0.1.40
The thing is, before MA routers can join 224.0.1.39, then need
to know
who the RP for that group is, also, before multicast routers can
join
224.0.1.40 to receive the RP information from MAs, they need to
know who
the RP for 224.0.1.40 is. Hence the old recursive design flaw
within
multicast technology. Before users join a group, they need who
the RP
is, and before they know who the RP is they need to joing the
group.
Hence, why some techies use sparse-dense-mode, so that for those
groups
which you don't know who the RP is, you just switch to dense
mode to
flood the traffic, (eg. cRPs using flooding of traffic to group
224.0.1.39, and MAs using flooding of traffic to group
224.0.1.40)
Another way to do this is to use sparse-mode (which you did),
but ip
auto-rp listener is disabled by default now, so you have to
enable it to
tell routers to turn on "DENSE" mode operation for only the 2
AUTO-RP
groups ... 224.0.1.39 and 224.0.1.40.
Your RPs need to flood 224.0.1.39 traffic to MAs, so MAs have to
join
that group, since they don't know who the RP is for 224.0.1.39,
they
then operate the group in dense mode. Similarly, your other
multicast
routers should join the 224.0.1.40, and understand how to flood
the
224.0.1.40 traffic as well in case there are downstream routers
who need
the information. Since they don't know who the RP for 224.0.1.40
is,
they then operate the group in dense mode.
NOTE: ip auto-rp listener doesn't flood traffic for all
multicast groups
there is, only for the auro-rp groups.
So to answer your question in a single statement:- YES, you need
to do
ip auto-rp listener for R3 and R5, if you're using sparse-mode
and
auto-rp for them. If you don't want to use auto-rp, then just
use
static-rp then (hardcoding who the RP is to them)
Many Thanks
Yemi Salau
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On
Behalf Of
Gupta, Gopal (NWCC)
Sent: Tuesday, December 04, 2007 9:25 AM
To: nhatphuc; Cisco certification
Subject: RE: IP PIM AutoRP Listener placement?
In my opinion you don't need coz, R1 will flood through dense
mode abt
RP and further R4 will do the same; provided that IP pim auto RP
is
configured on R1,R4 and R2 so, There should be no problem for R5
to
accept that info about the RP.
HTH
Gops
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On
Behalf Of
nhatphuc
Sent: Tuesday, December 04, 2007 14:44
To: Cisco certification
Subject: IP PIM AutoRP Listener placement?
Importance: Low
Hi Group,
My topology is like this:
R1------R2-----R3
|
|
R4
|
|
R5
PIM Sparse Mode is configured. R1 is Mapping Agent, R2 and R4
are cRP. I
choose to use ip pim autorp listener.
My opinion is: No need to configure ip pim autorp listener on R3
and R5.
My question: Do you have the same idea as me? Why/Why not?
Thank you
Phuc
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