[j-nsp] Proxmox with Multicast & Juniper EX

[Jeff Meyers]

Hi list,

I hope to get some experience and tips from you regarding the usage of a 
Proxmox cluster using Multicast in a (juniper-based) network. Since our 
multicast experience is quite low and was never required before Proxmox 
became quickly popular and is meanwhile widely used by our customer, we 
are a little stuck here. The situation is as follows:

Proxmox cluster communicates using multicast between the nodes being a 
member of the cluster. This works so far with the default configuration 
(igmp-snooping enabled on Juniper EX for all vlans, nothing further 
configured) if the nodes are on the same device. It is not working in 
the following setup:


                          MX480    MX80
                            |       |
                          +-----------+
                          | EX4550-VC |
                          +-----------+
       |--------------------|       |--------------------|
+-----------+                                     +-----------+
| EX4200-VC |                                     | EX4200-VC |
+-----------+                                     +-----------+
    |     |                                               |
Node 1   |                                             Node 3
        Node 2


Node 1 & Node 2 see each other but they don't see Node 3. It doesn't 
matter on which EX4200 Node 1 & 2 are placed, it always works locally 
but doesn't as soon as data has to travel through the EX4550 
core-switch. Most likely a solution would be to simply disable 
igmp-snooping on the EX4550 for the vlans, where I have to have a 
working multicast communication. I'd really like to avoid that since we 
are using vlan-range configurations instead of explicitly configuration 
each vlan but the latter is required, in order to disable igmp-snooping 
for just this specific vlan.

I am mostly confused why the packets passing the core makes a difference 
at all. For my understanding, igmp-snooping inspects the communication 
and passes multicast traffic to exactly those who shall receive it. Why 
isn't this working? I read that this requires an icmp querier. Would it 
help to configure that querier on one of the routers (it's two routers 
because of VRRP)? Can anyone explain why it is working on a local switch 
but not anymore as soon as a 2nd switch is involved in the path?


Hopefully some of you guys are working with setups like this as well and 
can help to solve our issue.


Thanks in advance!

Jeff