[j-nsp] Multicast PIM RP state

[Smith W. Stacy]

On Aug 25, 2010, at 3:26 PM, Chris Evans wrote:

> Hopefully someone can answer this..
> 
> I come from Cisco shop primarily and am comparing behaviors among Cisco and
> Juniper..
> 
> My question is thus.. I have multicast setup with Juniper and it is working,
> however I am having trouble verifying state when there is no subscribers to
> the group.. Basically my scenario is that I have a sender generating
> multicast traffic, but no receiver.
> 
> On Cisco, the RP maintains a *,G and S,G state for the group entries even
> when they are pruned. What I'm finding with Juniper devices is when the
> Juniper device is an RP is that when it Prunes it it totally removes any
> state of the multicast entry. As it removes any state I have no way of
> troubleshooting anything. Commands such as 'show pim join' and 'show
> multicast route' show nothing.
> 
> The Juniper device is not the first hop device in my topology..
> 
> My topology:
> Sender > L3 switch > Juniper Router (also RP) > Juniper Router > L3 switch
>> receiver.

You can view the register state on the RP using 'show pim rps extensive'. You should see register state for each (S,G) sending register packets.

user at rp> show pim rps extensive 
Instance: PIM.master
Address family INET

RP: 10.1.1.1
Learned via: static configuration
Time Active: 00:14:14
Holdtime: 0
Device Index: 132
Subunit: 32769
Interface: pd-0/0/0.32769
Group Ranges:
       224.0.0.0/4
Register State for RP:
Group           Source          FirstHop        RP Address      State    Timeout
224.1.1.1       10.210.58.8     10.0.0.1        10.1.1.1        Receive      269   <<<<<<<<<<<<<<<<

Address family INET6


FWIW, you can also simulate a receiver using the static IGMP group configuration. Something like:

[edit protocols igmp]
user at rcvr# show 
interface fe-0/0/0.0 {
   static {
       group 224.1.1.1;
   }
}

This does NOT send any IGMP packets on the wire, but it simulates the state that would be created if the router received a (*,224.1.1.1) IGMP group membership report from some host on the fe-0/0/0.0 interface.

--Stacy