From: Edwards, Andrew M (andrew.m.edwards@boeing.com)
Date: Tue Feb 08 2005 - 14:26:36 GMT-3
Depends upon what you are trying to do exactly, but a combination of
mroutes and tunnels would be required for the hub to continue the RPF
towards a downstream spoke receiver.
One way:
Build a tunnel towards the source of the DM group. Do NOT enable pim
dense-mode on the source for the DM groups serial interface. Only
enable pim dense-mode on the tunnel between the source and the hub
tunnel interfaces.
Now, enable pim dense mode on the hub frame interface and the receiving
spoke frame interface.
If you do this, then you don't need mroutes because the source of the DM
group is through the tunnel and traffic would be arriving on the tunnel
thereby passing the RPF. As long as the hub frame interface is in the
OIL for the parent (*,G) then it will forward along the downstream path
towards the receiving spoke.
Another way:
Build a tunnel between the receiving spoke and the hub. Enable pim
dense-mode on all frame interfaces and on the tunnel between the hub and
receiving spoke router. On the receiving spoke use a static mroute that
points towards the source of the DM traffic such that the next hop is
the other end of the tunnel interface. This will pass the RPF for the
spoke receiver.
And to answer your final question, the RPF is done towards the source
for dense-mode traffic and towards the RP for sparse-mode (excluding the
RP-Prune).
So, if the question was to source dense mode traffic from 1.1.1.1
towards the 255.5.5.5 group, the mroute would be a (1.1.1.1, 255.5.5.5)
entry. And, if the next hop up the RPF was 2.2.2.2, you would have a
static mroute such as:
Ip mroute 1.1.1.1 255.255.255.255 static 2.2.2.2
Then a show ip mroute will indicate that the (1.1.1.1,255.5.5.5) as
MROUTE. <- indicates static mroute.
Just remember that when it comes to multicast, static mroutes and
tunnels are your friends.
HTH,
Andy
-----Original Message-----
From: eDu [mailto:eeduuu@hotmail.com]
Sent: Tuesday, February 08, 2005 12:18 AM
To: ccielab@groupstudy.com
Subject: multicast question
Hello everybody.
I passed the beta written exam (it was pretty difficult) and now I'm
starting up with the lab. I've got a question for you. If I have 3
routers connected in a multipoint frame-relay, in a hub-and-spoke
manner, and I configure PIM DM between them, I have a problem. The
problem is that the hub router receive the traffic from one of the
spokes, but it doesn't send it to the other. I think it's not possible
to add the same interface to both incoming and outgoing interface list.
The first solution I guess is the use of gre tunnels. The second one is
to configure static mroutes, but I don't know what routes.
Sure you've seen this scenario before. Any idea?
R1
|
__________|__________
| |
R2 R3
|
|
Multicast
source
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