Hi Donald,

Thank you very much for your feedback.

> SSM should work, configure the interface(s) with `ip pim ssm` and make
> sure you have a ssm range specified via the `ip pim ssm prefix-list
> <plistname>` if doing beyond the default SSM range.

Under the interface configuration I can only typ "ip pim sm" for the sparse mode.
Do you mean this or do I have a missing option 'ip pim ssm'?

For a better understandig, my topology are two centos 7 linux hosts. One sitting int 'Colo1' [10.190.0.22] and one in 'Colo2' [10.55.0.33]. They have a direct MPLS link. This Link is Ipsec encapsulated (Strongswan) and has a GRE Interface for Multicast support. Each Linux Host is connected via Layer 3 Transferlink (BGP Relation) to the inside LAN Arista Switches, where the multicast sender and receiver are connected.
All switches are PIM-SM SSM enabled.

Currently the receiver is in Colo1 [10.190.0.22] and the sender in Colo2 [10.55.0.33]


>`show ip multicast`

Colo1:
-----

Mroute socket descriptor: 7(Default-IP-Routing-Table)
Mroute socket uptime: 19:50:34

Zclient update socket: 10 failures=0
Zclient lookup socket: 13 failures=0

Maximum highest VifIndex: 31

Upstream Join Timer: 60 secs
Join/Prune Holdtime: 210 secs
PIM ECMP: Disable
PIM ECMP Rebalance: Disable

RPF Cache Refresh Delay: 50 msecs
RPF Cache Refresh Timer: 0 msecs
RPF Cache Refresh Requests: 2
RPF Cache Refresh Events: 2
RPF Cache Refresh Last: 00:52:38
Nexthop Lookups: 7
Nexthop Lookups Avoided: 0

Scan OIL - Last: 00:52:38 Events: 2
MFC Add - Last: 00:00:24 Events: 5
MFC Del - Last: 00:00:56 Events: 2

Interface Address ifi Vif PktsIn PktsOut BytesIn BytesOut
Colo1:Colo2 172.21.21.75 16 0 0 0 0 0
ens4f1.308 172.22.190.10 12 1 0 0 0 0


Colo2:
-----

Mroute socket descriptor: 7(Default-IP-Routing-Table)
Mroute socket uptime: 46:01:22

Zclient update socket: 10 failures=0
Zclient lookup socket: 13 failures=0

Maximum highest VifIndex: 31

Upstream Join Timer: 60 secs
Join/Prune Holdtime: 210 secs
PIM ECMP: Disable
PIM ECMP Rebalance: Disable

RPF Cache Refresh Delay: 50 msecs
RPF Cache Refresh Timer: 0 msecs
RPF Cache Refresh Requests: 16
RPF Cache Refresh Events: 13
RPF Cache Refresh Last: 19:40:22
Nexthop Lookups: 743
Nexthop Lookups Avoided: 0

Scan OIL - Last: 19:40:22 Events: 13
MFC Add - Last: --:--:-- Events: 0
MFC Del - Last: 00:02:32 Events: 371

Interface Address ifi Vif PktsIn PktsOut BytesIn BytesOut
Colo2:Colo1 172.21.21.76 21 0 0 0 0 0
eth0 172.24.37.3 2 0 0 0 0 0
pimreg 0.0.0.0 45 0 0 0 0 0

>`show ip pim upstream`

Colo1:
-----

Iif Source Group State Uptime JoinTimer RSTimer KATimer RefCnt
Colo1:Colo210.55.0.33 232.122.14.42 J 00:01:00 00:00:40 --:--:-- --:--:-- 1

Colo2:
-----

Iif Source Group State Uptime JoinTimer RSTimer KATimer RefCnt
eth0 10.55.0.33 232.122.14.42 J 00:02:35 00:00:04 --:--:-- --:--:-- 1

>`show ip mroute`

Colo1:
-----

Source Group Proto Input Output TTL Uptime
10.55.0.33 232.122.14.42 PIM Colo1:Colo2 ens4f1.308 1 00:01:24

Colo2:
-----

Source Group Proto Input Output TTL Uptime

>I personally am a bit interested in the rpf for 172.24.37.3 `show ip rpf 172.24.37.3`.

For a better debuging I changed the sender 172.24.37.3 to another host. This was on the FRR Host before. The new IP is 10.55.0.33.
I did this command on the host in Colo2 (closer to the sender).

# sh ip rpf 10.55.0.33
Routing entry for 10.55.0.0/24 using Unicast RIB
Known via "bgp", distance 200, metric 0, best
Last update 1d22h03m ago
* 172.24.37.102, via eth0

If you need any further debug output feel free to ask. Thank you very much for helping on this issue.

greetings,
Jonas