What are the required networks (physical and virtual) for a 3-node VMM cluster?

Swisher Sweet

11/14/23, 2:15 PM

I'm setting up a 3-Node Synology Virtual Machine Manager cluster and I am unclear on how to properly setup the dedicated cluster network vs other networks. I've read through all of Synology's guides and spent hours searching for blog posts or YouTube videos that describe how to do this, but there is no good documentation on how to properly setup the network for this cluster.

I realize not a lot of people use this feature, but since this topic is in-scope for this site and there's a [synology] tag, I thought I'd see if the kind folks here can help me.

I just re-read this article:

https://kb.synology.com/en-id/DSM/help/Virtualization/getting_started?version=7

The documentation isn't very clear. Here's what I think I understand... In a 3-node cluster, I would need to have 2 networks:

LAN 1 (192.x.x.x), which will be the "Default VM Network", and
LAN 2 (10.x.x.x), which will be my "Dedicated Cluster Network".

However, how do I tell VMM which network is my "Dedicated Cluster Network" and which one is used for services?

Also, do these networks have to be on completely different physical switches, or do I need to setup separate VLANs for the two networks on the same switch, or can they just share a standard switch without setting up VLANs?

Note, in this setup, this cluster will not have a heavy network load.

Has anyone else setup one of these before and able to describe how I should be setting up the networks?

Thank you.

131

1 + 2

synology

Swisher Sweet

11/14/23, 2:27 PM

Hi there, if you are going to vote down my question, would you mind at least letting me know in a comment how I can improve it?

Chopper3

11/14/23, 3:10 PM

It wasn't my downvote but your post is very basic and seems like you've not done the basic research we'd expect question askers here to have done. Basically you've walked into the pilot's lounge at an airport asked "how metal bird in sky?"

Score:0

Server

Swisher Sweet

11/20/23, 11:51 AM

When you first install VMM on Synology, it creates a "Default VM Network". This network, unless you change it and/or have needs beyond what this single virtual network can provide is all that is needed or required (according to Synology) to setup a 3 node cluster.

However, it is recommended that you setup another physical network or VLAN on a different subnet, completely independent and inaccessible from the "Default VM Network". This "Cluster Network" will be used for inter-cluster communication only, such as replication and migrations. It's important to note that this will not (and should not) be found under the "Network" tab in the VMM administration console. The "Default VM Network" should not have selected any of the NICs that the "Cluster Network" will use.

When add a second host, there's a step in the add host wizard which asks you to "Select a Network". It gives no explanation of what this network is used for, but it's for the "Cluster Network". After you choose that network, all hosts will communicate on that network for inter-cluster communication.

It took days of back and forth support emails and a phone call with Synology to figure this out, so I'm hoping this answer saves other folks some time.

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