From: Lord, Chris (chris.lord@lorien.co.uk)
Date: Tue Aug 10 2004 - 13:30:25 GMT-3
Tim,
My understanding of its purpose is slightly different - but I'm not 100% either.....
Suppose R1, R2 and R3 are all running sparse mode with static RP where the RP is at the hub or upstream of it - simple enough.
When R1 pushes mcast packets out of its serial nbma interface then by default they will be sent to both dlcis and hence to both R2 and R3, provided "either one of them" has clients. This can result in unnecdessary traffic going to either R2 or R3 if no clients exist on one of them. pim nbma mode changes this default behaviour so that packets only get sent to R1 or R2 if they have active clients on them.
Chris.
-----Original Message-----
From: ccie2be [mailto:ccie2be@nyc.rr.com]
Sent: Tuesday, August 10, 2004 5:13 PM
To: jongsoo.kim@intelsat.com; ccielab@groupstudy.com
Subject: Re: Regarding "ip pim nbma-mode"
JK,
You are correct. Only R1 does need this command.
RE: your 2nd question, consider this.
Let's assume that the mcast domain is operating in Dense mode. In this
case, R1 will only prune the mcast stream when the last downstream mcast
receiver sends a prune. If a prune is sent by R2 to R1 but R3 still needs
to receive mcast traffic, R1 will ignore the prune and continue to send.
So, that's why nbma mode isn't needed with dense mode.
Now, sparse-dense mode might be a different matter. The way I understand
it, this mode is only needed when running Auto-RP because then the auto-rp
groups 224.0.0.39 and .40 run in dense mode but the other groups run in
sparse mode.
Now, I'm not 100% positive, but I would use the nbma mode command in this
situation because I wouldn't want the mcast groups running sparse mode to
have their traffic cut off when the hub gets a prune message.
One thing you have to keep in mind is that if you're running Auto-rp, the MA
must be either on the hub or upstream of the hub because if it's on a spoke
then other spokes won't get the group - rp mappings sent out by the MA. The
RP can be behind a spoke. That's OK as long as the MA is reachable by the rp
announce messages.
HTH, Tim
----- Original Message -----
From: <jongsoo.kim@intelsat.com>
To: <ccielab@groupstudy.com>
Sent: Tuesday, August 10, 2004 11:18 AM
Subject: Regarding "ip pim nbma-mode"
> The way I understand this commnad is to enable somewhat multicast
capability on NBMA link such as F/R PVC.
>
> This is my interpretation.
> So let's say R1,R2,R3 are PIM neighbor, if R1 connected to R2 and R3 via
multipoint PVC using hub and spoke, then by using this command, R1 can send
multicast to R2 and R3, which of course should be two identical multicast
traffic stream but with different DLCI.
>
> If this is the case, I think only R1 needs this commnad as R1 is HUB and
R2 and R3 are spoke.
>
> Am I in a right track on this??
>
>
> Also, I can't figure out why sparse-dense mode shouldn't use this command.
>
>
> Thanks folks
>
> JK
>
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