From: alsontra@hotmail.com
Date: Fri Feb 06 2004 - 00:34:52 GMT-3
Don't mean to grind this one into the ground, but....
In looking at my neighbor tables I noticed that within my NBMA there exists
a DR. This DR was obviously selected because of its IP 141.1.1.6. 141.1.1.6
is a spoke router, so I change hub routers ip to 141.1.1.7 and instantly it
becomes the DR.
Topology is a simple NBMA
R5(141.1.1.5)<------ (changes to 141.1.1.7, to make it DR)
- -
- -
R6(141.1.1.6) R2(141.1.1.2)
Show ip pim nei on R5 produces
PIM Neighbor Table
Neighbor Address Interface Uptime Expires Ver Mode
141.1.1.2 Serial0/2 00:31:32 00:01:01 v1 Sparse
141.1.1.6 Serial0/2 00:31:36 00:01:26 v1 Sparse
(DR)
191.1.1.47 Tunnel0 05:42:52 00:01:31 v2
So, I change the IP on the hub to make it DR, and it works....
Show ip pim nei on R6 produces
PIM Neighbor Table
Neighbor Address Interface Uptime Expires Mode
141.1.1.7 Serial0 00:01:55 00:01:04 Sparse-Dense (DR)
<-----Hub is now DR
Conclusions: there is a DR election on NBMA, but what does this mean? Both
spokes use the RP address to join multicast groups?
Regards,
Alsontra
----- Original Message -----
From: "Scott Morris" <swm@emanon.com>
To: "'Michael Snyder'" <msnyder@revolutioncomputer.com>;
<ccielab@groupstudy.com>
Cc: "'Hossam'" <sam6626@yahoo.com>; <alsontra@hotmail.com>
Sent: Thursday, February 05, 2004 4:53 PM
Subject: RE: Multicast over NBMA again!
> You also have the BSR functionality which is niether Dense nor Sparse in
its
> implementation.
>
> As for the "ip pim dr-priority" the effect would be a little odd here.
The
> PIM DR is based on a routers' relationship to a multicast source. PIM
> Sources, or the local DR will send PIM-Register messages to an RP. So I'm
> thinking this command is serving a different function then what you are
> trying to talk about here, because it has no bearing on a router being an
RP
> or forwarding RP information on!
>
> HTH,
>
>
> Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713, CISSP,
> JNCIS, et al.
> IPExpert CCIE Program Manager
> IPExpert Sr. Technical Instructor
> swm@emanon.com/smorris@ipexpert.net
> http://www.ipexpert.net
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Michael Snyder
> Sent: Thursday, February 05, 2004 7:33 PM
> To: ccielab@groupstudy.com
> Cc: 'Hossam'; alsontra@hotmail.com
> Subject: RE: Multicast over NBMA again!
>
> I could be wrong, but I remember that auto-rp doesn't work without
> sparse-dense mode. How could it, it uses multicast to advertise the rp
> groups? Chicken and egg problem.
>
> So, if you use sparse mode, you have to use a static rp.
>
> Auto-rp has to have sparse-dense mode to function.
>
> Sparse-mode will work fine with static rp.
>
> One more thing, on the multipoint frame-relay (or even multipoint isdn)
>
> Run ip pim nbma-mode on the interfaces
>
> And on the hub interface run the following command,
>
> ip pim dr-priority 1000
>
> Why? Same reason you make the ospf process the highest priority on the
hub
> interface, it can speak to all the spokes.
>
> interface Serial0.56 multipoint
> ip address 172.16.56.2 255.255.255.248
> ip pim dr-priority 1000
> ip pim nbma-mode
> ip ospf hello-interval 2
> ip ospf priority 255
> frame-relay map ip 172.16.56.2 105
> frame-relay map ip 172.16.56.5 105 broadcast frame-relay map ip
> 172.16.56.6 106 broadcast
>
>
> I could be wrong on some this, your mileage may vary, but the above
> config(s) have worked well for me in practice labs.
>
>
> -----Original Message-----
> From: alsontra@hotmail.com [mailto:alsontra@hotmail.com]
> Sent: Thursday, February 05, 2004 7:49 PM
> To: Hossam
> Cc: ccielab@groupstudy.com
> Subject: Re: Multicast over NBMA again!
>
> Sorry about that. I was running a similar configuration yesterday, and
there
> are a few things I notice right off about yours. Sparse-dense mode is not
> recommended for NBMA interfaces, I think sparse should be used. Also you
> need to issue the ip pim nbma-mode command on the serial interfaces( I
used
> this command on all NBMA attached interfaces)
>
> ip pim nbma-mode <------This allows multipule mappings on your serial ip
> pim sparse-mode
>
> After you've add those, I would verify that the RP address is registering
> with the spoke clients.
>
> (sh ip pim rp )
>
> Should look like this: Group: 228.1.1.1, RP: 223.1.1.2, v1, uptime
04:01:38,
> expires 00:03:18
>
> There are some exellent post regarding this topic, do a search for Brian
> McGahan's last post regarding multicast.
>
> Hope this helps,
> Alsontra
>
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