From: nhatphuc (nhatphuc@gmail.com)
Date: Tue Dec 04 2007 - 11:18:13 ART
So the answer is NO NEED to configure autorp listener on edge routers (R3
and R5), but it is recommended to do that for scalability.
Thanks again for all of your replies
Phuc
On Dec 4, 2007 8:30 PM, shiran guez <shiranp3@gmail.com> wrote:
> 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 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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> > >
> > >
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> > _______________________________________________________________________
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>
>
>
> --
> Shiran Guez
> MCSE CCNP NCE1
> http://cciep3.blogspot.com
> http://www.linkedin.com/in/cciep3
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