From: null void (nullv0idmain@yahoo.com)
Date: Fri Feb 04 2005 - 14:19:18 GMT-3
Intersting statements on the book you cited LabCCIE in the prac study 2 book on page 247 of the lab 6 prac lab , they are stating since R5 , R6 and R13 are a multipoint frame network segment , all routers on there frame relay interfaces have ip pim nbma-mode on them .. The way it is stated I am assuming they are saying anytime you have a multipoint frame relay interface and are running multicast to spoke routers use the nbma-mode command.. I was under the impression we only needed it sometimes , such as when a hub / multipoint router needs multicast streams to go to say 3 of its spoke routers , in this situation I can see this .. But if I only have one spoke that is multicast enabled I dont think it is required , the only thing I have noticed is that since you dont put that command ip pim nbma-mode on the hub when you ping multicast groups , assuming they are pingable , then you only get 1 reply back I am assuming this is due to being fastswitched ??
Labcciee <labccie@uol.com.br> wrote:Yes, thats the explanation I found in the CCIE Practical Studies volume II.
If one othe spoke routers request the hub to stop sending milticast traffic to
it, withou the command "ip pim nbma-mode" the others hub connected to the same
phisical interface will stop receiving multicast traffic too.
If the others hub are not reciving any multicast trafficc, i think there will
be no problem.
----- Original Message -----
From: null void
To: Labcciee ; ccielab@groupstudy.com
Sent: Friday, February 04, 2005 2:46 PM
Subject: Re: Requirement details of "IP PIM NBMA"
Thanks for the reply... I will read that section but on the docCD
http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122cgcr/fip
r_c/ipcpt3/1cfmulti.htm#21887
the way they are explaining it is that the purpose of "ip pim nbma-mode" is
for efficiency of the link . So if your Multipoint Hub interface running ip
pim sparse-mode .. Has its framerelay interface maps configured with broadcast
feature on each map statement to say 4 spoke routers... ip pim nbma-mode
reduces unneed traffic so if only spoke1 requested to join a group , ip pim
nbma-mode will when receiving traffic for that group send it to that one
neighbor who requested it not to the other 3... But you are saying that if one
of the other spokes was receiving the stream earlier but then sent a request
to stop sending the stream then all spokes will now not receive the multicast
stream ?? What if your in a situation in which out of 3 spokes only 1 of
those spokes has multicast enabled the other 2 do not have any muliticast
configured on them at all , at that point it would not be needed then correct
? Your saying that if multiple spokes are joined to a group , then one of them
says stop , it affects all spokes becuase they are all connected into the HUB
routers physical interface ??
Null..
Labcciee wrote:
Hi,
The "ip pim nbma-mode" must be configured on subinterfaces running frame
relay multipoint mode.
It's required because without it, with the reouter receives a prune
message
on the phisical interface it could cut off the multicast traffic for all
others subinterfaces. This explanation is on the CCIE Practical Studies
volume II
----- Original Message -----
From: "null void"
To:
Sent: Friday, February 04, 2005 2:18 PM
Subject: Requirement details of "IP PIM NBMA"
> Say we have the following topology:
>
> R1 - is the hub of frame relay hub-spoke toplogy. Serial 0/0.1
multipoint
goes to 2 spoke routers R2 , R3. Serial 0/1.1 point-to-point goes to R6's
S0/1 this is frame-relay circuit also
>
> R6 - is a standalone stub router with a point to point se rial sub
interface off of Ser0/1 to R1's S0/1
>
> R3 - Ser0/0 physical interface connects into R1 the frame relay hub
router's s0/0.1 multipoint so R3 , R2 and R1 are all layer 3 reachable on
same ip subnet in hub spoke topology.
>
> If we configure say R3 as RP on its loopback 0 interface for all
groups.
Then configure ip pim sparse-mode on all interfaces of R3 , R6 , R1 . So
now
R3 , R6 and R1 see each other as pim neighbors and the RP is found being
hardcoded to R3 loopback . Is IP PIM NBMA mode required on R1's S0/0.1
multipoint and s0/1.1 point to point interfaces ?? Without it I can still
from all multicast enabled routers , in this case being R3 , R6 and R1
ping
the groups that we configured onto R6's Loopback 0 interace via the ip
igmp
join-group x.x.x.x command so it is working ... But my question is when
is
ip pim nbma requried and why ??? Any resources / docs on this would be
greatly appreciated... TIA Null
>
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