question about PIM Auto-RP MA !!

[mohammed hashim]

Hi,

I have noticed that when we configure MA, all of its PIM neighbors install (*,224.0.1.39) and (S , 224.0.1.39), 

but any routers behind these neighbors will not, they will only install (*,224.0.1.40) and (S , 224.0.1.40),

is there any specific reason for this?

[Georg Pauwen]

Hello,

post the configs of the routers involved...

[mohammed hashim]

please see the attachment,

there are three routers,

R8 is the MA,

R9 has direct connection to R8, this one has (*,224.0.1.39) and (S,224.0.1.39)

R13 is not directly connected to MA, and it has no information about 224.0.1.39

I do not have issue of R13 does not install this info, but why only directly connected routers does that !?

I tried to work on the topology by changing positions of MA and RPs and got always same results.

R9#show ip mroute 224.0.1.39 | beg 224
(*, 224.0.1.39), 00:33:50/stopped, RP 0.0.0.0, flags: DC
Incoming interface: Null, RPF nbr 0.0.0.0
Outgoing interface list:
GigabitEthernet1.129, Forward/Sparse, 00:33:50/stopped
GigabitEthernet1.119, Forward/Sparse, 00:33:50/stopped
GigabitEthernet1.89, Forward/Sparse, 00:33:50/stopped

(12.12.12.12, 224.0.1.39), 00:33:50/00:01:26, flags: T
Incoming interface: GigabitEthernet1.129, RPF nbr 10.0.129.12
Outgoing interface list:
GigabitEthernet1.89, Forward/Sparse, 00:33:50/stopped
GigabitEthernet1.119, Forward/Sparse, 00:33:50/stopped

R13#show ip mroute 224.0.1.39 | beg 224
Group 224.0.1.39 not found

Multicast topology working without issues,

[paul driver]

Hello

The reason being is you are using sparse-mode and 224.0.1.39 and 224.0.1.40 can only work in dense mode for it to register with a RP, If it doesn't know where the RP it wont be able to join the MC group.

You would see *.224.0..1.39 if you enable sparse-dense mode on the interfaces as it will revert to use dense mode to find the RP and to allow the flooding of both this groups

The reason why is it working in your topology which is running in sparse mode is because you have Auto-rp listener enabled on the routers, which doesn't need dense mode or sparse-dense mode configured on the interfaces to work.

Auto-rp listener - allows 224.0..1.39, 224.0..1.40 to be flooded just like dense mode thus the rtrs are able to register and obtain a rp group mapping

Lasty - Without auto-RP-listener and dense mode flooding , I guess you would only see *.224.0..1.39 on pim interfaces directly connected to the MA or on the same shared network segment to the MA

res
Paul

[paul driver]

Hello

(*,224.0.1.40) and (S , 224.0.1.40),  -  you;ll see this when you just enable pim on a interface , doesnt even require a pim neighbor relationship

(*,224.0.1.39) and (S , 224.0.1.39) - - this is when as you have rightly stated, you specified a MA and this discovery msg is then flooded to other pim neighbors

but any routers behind these neighbors will not

Do these routers have a connected pim enabled interface to the upstream routers?

res
Paul