From: Gupta, Gopal (NWCC) (gopal.gupta@hp.com)
Date: Tue Dec 04 2007 - 14:14:15 ART
Hi All,
There is one question, am scratching my head
Topology
R5->R1->R4->R3->R2
R4 is MA and R3 is RP
Question is w/o using IP Pim autorp listener and all interfaces in
Sparse mode, R4 is still sending the group-RP mappings to all the
Routers including R5; is this the default behavior ??
The problem is R5 should not recv these mappings from R4 coz all is
running in Sparse mode.
R5:-->
R5#sh ip mr
(*, 224.0.1.40), 01:10:44/stopped, RP 0.0.0.0, flags: DCL
Incoming interface: Null, RPF nbr 0.0.0.0
Outgoing interface list:
Serial1/0.504, Forward/Sparse, 01:10:44/00:01:32
(204.12.1.4, 224.0.1.40), 01:10:43/00:02:54, flags: PLTX
Incoming interface: Serial1/0.504, RPF nbr 155.1.15.1
Outgoing interface list: Null
R5#sh ip pim rp ma
PIM Group-to-RP Mappings
Group(s) 224.0.0.0/4
RP 150.1.3.3 (?), v2v1
Info source: 204.12.1.4 (?), elected via Auto-RP
Uptime: 01:10:47, expires: 00:02:49
As far as i have studied till now is we need either PIM Sparse-dense
mode or pim AutoRP Listener for getting group to RP mappings and it is
working W/O those commands.
Hope you will throw some light on this.
Many Thanks,
Gops
________________________________
From: shiran guez [mailto:shiranp3@gmail.com]
Sent: Tuesday, December 04, 2007 19:01
To: nhatphuc
Cc: Salau, Yemi; Gupta, Gopal (NWCC); Cisco certification
Subject: Re: IP PIM AutoRP Listener placement?
well the ip pim autorp listener is enabling the router to use dense-mode
only for the 224.0.1.39 and 224.0.1.40 this will in result cause the
router to flood pim out of the pim enabled interfaces in the router,
the ip pim autorp listener is actually a little misleading command as it
is not listening it is flooding dense mode traffic for the 2 dense mode
groups of the auto rp and mapping agent
each router in the pim even if he is set with ip pim sparse-mode on the
interface he will accept any pim traffic that is sent to him.
so this mean that R5 will get the mapping agent traffic he just want be
able to flood to the next down neighbor if he had one and this is why it
is not needed.
it is recommended to put this command on all routers.
On Dec 4, 2007 2:48 PM, nhatphuc <nhatphuc@gmail.com> wrote:
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
<http://224.0.1.39/> and 224.0.1.40 <http://224.0.1.40/>
> across interfaces operating in PIM sparse mode. I believe you
know cRPs
> uses 224.0.1.39 <http://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
<http://224.0.1.40/>
>
> The thing is, before MA routers can join 224.0.1.39
<http://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 <http://224.0.1.40/> to receive the RP information
from MAs, they need to know who
> the RP for 224.0.1.40 <http://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 <http://224.0.1.39/> , and MAs using flooding of
traffic to group 224.0.1.40 <http://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 <http://224.0.1.39/> and 224.0.1.40
<http://224.0.1.40/> .
>
> Your RPs need to flood 224.0.1.39 <http://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
<http://224.0.1.39/> , they
> then operate the group in dense mode. Similarly, your other
multicast
> routers should join the 224.0.1.40 <http://224.0.1.40/> , and
understand how to flood the
> 224.0.1.40 <http://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 <http://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
<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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