From: nhatphuc (nhatphuc@gmail.com)
Date: Tue Dec 04 2007 - 09:48:23 ART
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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