From: Mathew Fernando (mathewfer@gmail.com)
Date: Tue May 16 2006 - 23:23:18 ART
Hi Chris/Jian,
Thank you for the below.
Both of you have answered my question EXACTLY.
Also thank you for others who was trying to answer my question.
As always, this list is EXCELLENT.
mathew.
On 5/17/06, Chris Lewis <chrlewiscsco@gmail.com> wrote:
>
> Essentially each interface you enable for PIM will do an igmp join to
> 224.0.1.40, so for directly connected routers you do not need any dense
> mode support for that group. This will be seen in the mroute table as the
> following entry. The join to this group is a Cisco specific thing for
> auto-RP.
>
> (*, 224.0.1.40), 02:56:58/00:02:00, RP 0.0.0.0, flags: DCL
> Incoming interface: Null, RPF nbr 0.0.0.0
> Outgoing interface list:
> FastEthernet0/0, Forward/Dense, 02:56:58/00:00:00
>
> Interestingly if you have sparse mode from the hub to the spokes, the igmp
> join enables the multicast routing to have teh spokes learn of the RP, if
> you then enable dense mode between the spokes and teh routesr behind the
> spokes, those routers should also learn about the RP.
>
> Chris
>
>
> On 5/16/06, Jian Gu <guxiaojian@gmail.com> wrote:
>
> > Shivjit,
>
> I don't think you were answering what Mathew is asking.
>
> The reason spokes can get the RP address even without auto-rp listener
> configured is because the spokes are directly connected to RP. (I vaguely
> remember Chris Lewis had a very good explaination about this, please
> search
> archieve for it)
>
> What is your point of configure static rp with an access-list to allow
> auto-rp groups? firstly, static RP might not be allowed, secondly, by
> default "ip pim rp-address" will include the whole multicast address space
> 224.0.0.0/4.
>
> On 5/16/06, Shivjit Patil < shivjitp@yahoo.com> wrote:
> >
> > To configure Auto-RP in a sparse-mode env do the following
> >
> > 1) Configure rp address for the global groups on all the routers
> > participating in multicast using the following command
> > ip pim rp-address x.x.x.x 1
> > access-list 1 permit 224.0.0.39
> > access-list 1 permit 224.0.0.40
> >
> > 2) Configure the rp address for the local groups on the RP router
> using
> > ip pim send-rep-announce lo 0 scope 16 group-list 1
> > access-list 1 permit 239.0.0.0 0.255.255.255
> >
> > 3) Configure the rp mapping agent on another router that has good
> > connectivity to all routers in the multicast domain using
> > ip pim send-rp-discover scope 16
> >
> > All the interfaces should have "ip pim sparse-mode" configured.
> >
> > So the difference between sparse-mode and sparse-dense-mode is that we
>
> > need to define the rp address for the default groups on all the routers.
> >
> > Also keep in mind that when you are deploying this over a frame-relay
> > network on the hub router configure " ip pim nbma-mode" to allow it to
> > distribute the rp mappings to all its spokes.
> >
> > HTH
> > Shiv
> >
> > Mathew Fernando <mathewfer@gmail.com> wrote:
> > Hi Group,
> >
> > I setup a LAB scenario with a hub-and-spoke topology where there are 3
> > spoke
> > routers and 2 of the spokes has another router behind.
> > The hub router uses FR sub-interfaces for 3 spoke routers.
> >
> > RIP is configured on all the interfaces on all the routers and PIM
> SPARSE
> > mode is configured on all the interfaces.
> > AUTO-RP is configured on the HUB router who acts as the RP as well as
> the
> > mapping agent. No filters are applied for the groups in RP or mapping
> > agent
> > configs.
> >
> > When I say "show ip pim rp mapping", it shows the RP IP (of the hub
> > router)
> > on all the spoke routers except on the 2 routers behind the spoke
> routers.
> >
> > MY QUESTION IS: I do not understand how these 3 spoke routers learn the
> > AUTO-RP when there is no DENSE mode (or sparse-dense) configured.
> >
> > Also the command "ip pim autorp listener" is not configured on any of
> the
> > routers. I understand why these 2 routers behind the spoke does not see
> > the
> > AUTO-RP (because there is no DENSE configured). IOS on all the routers
> are
> > 12.2T.
> >
> > Can someone please explain how this works?
> >
> > Thanks in advance
> >
> > mathew
> >
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