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[Junos] Verify the status of the PIM join

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Article ID: KB21903 KB Last Updated: 08 May 2020Version: 3.0
Summary:

This article shows how to verify the status of a PIM join and that it has the correct upstream and downstream interfaces.

 

Symptoms:

When troubleshooting a Multicast issue in KB21586 - Resolution Guide - Troubleshoot Multicast issue with Junos OS device configured as Layer 3 (running PIM protocol), you need to verify the state of the PIM join on the device. Also, you want to verify that the upstream and downstream interfaces for the PIM join are correct.

The following Network Topology is referenced in the solution:

Note: Refer to KB21591 - Sample Multicast Network Topology with Junos OS devices for locating the LHR and RP and for definitions of the components.

 

Solution:

Run the following commands to check the status of the PIM join on the device.

root@LHR> show pim join inet <group address>
root@LHR> show pim join extensive inet <group address>

Below is an example of the expected output for the network topology above.

LHR

root@LHR# run show pim join inet 224.100.100.100
Instance: PIM.master Family: INET
R = Rendezvous Point Tree, S = Sparse, W = Wildcard

Group: 224.100.100.100
    Source: 192.168.200.10
    Flags: sparse,spt
    Upstream interface: ge-0/0/20.0

root@LHR# run show pim join extensive inet 224.100.100.100
Instance: PIM.master Family: INET
R = Rendezvous Point Tree, S = Sparse, W = Wildcard

Group: 224.100.100.100
    Source: 192.168.200.10  <---- Multicast stream sent by server (If *, it received join from downstream neighbor) 
    Flags: sparse,spt
    Upstream interface: ge-0/0/20.0   <----
    Upstream neighbor: 192.168.20.2   
    Upstream state: None, Join to Source
    Keepalive timeout: 345
    Downstream neighbors:      
        Interface: irb.100           <----
            192.168.100.1 State: Join Flags: S   Timeout: Infinity

The above output on the LHR shows that it has received the (S,G) from the Upstream interface ge-0/0/20, sent by neighbor 192.168.20.2. (Source 192.168.200.10, Group 224.100.100.10).

If the source is *, the status is (*,G). This means that the Multicast stream has not reached the device. The PIM router has received the PIM join from its downstream neighbor and it is connected to the RP. The upstream interface should be the L3 interface towards the RP. The "downstream neighbors" should list all the L3 interfaces towards the Multicast receivers that are requesting the traffic for the specific group (that is, irb.101, irb.102).

RP

root@RP1# run show pim join inet 224.100.100.100
Instance: PIM.master Family: INET
R = Rendezvous Point Tree, S = Sparse, W = Wildcard

Group: 224.100.100.100
    Source: 192.168.200.10
    Flags: sparse,spt
    Upstream interface: ge-0/0/15.0
    root@RP1# run show pim join extensive inet 224.100.100.100
Instance: PIM.master Family: INET
R = Rendezvous Point Tree, S = Sparse, W = Wildcard
Group: 224.100.100.100               Source: 192.168.200.10   <---- Multicast stream sent by server  (If *, there is no source for that group)
    Flags: sparse,spt
    Upstream interface: ge-0/0/15.0  
    Upstream neighbor: 192.168.15.2
    Upstream state: None, Local RP, Join to Source
    Keepalive timeout: 304
 Downstream neighbors:         
       Interface: ge-0/0/20.0      
            192.168.20.1 State: Join Flags: S Timeout: 192

The above output on the RP shows that it has received the (S,G) from the Upstream interface ge-0/0/15, sent by neighbor 192.168.15.2. (Source 192.168.200.10, Group 224.100.100.10).

If the source is *, the status is (*,G), which means that the FHR has not registered the source to the RP, and the Multicast stream (traffic) is not flowing to the RP.

For an explanation of the fields in the "show pim join" and "show pim join extensive" commands, refer to show pim join.

 

Modification History:

2020-05-08: Article reviewed for accuracy; no changes required; article valid and accurate

 

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