topic Re: Why A3 needs to be deployed in odd numbers and how to make resilient across two DC's in ExtremeCloud A3

Why A3 needs to be deployed in odd numbers and how to make resilient across two DC's

Anonymous — Sun, 31 Jan 2021 18:25:57 GMT

Hi,

The A3 has to be deployed in odd number like 1,3,5,7 etc, which I believe is a requirement placed on the underlying PacketFence product.

Also believe it might be related to requiring from a clustering point of view that 2 nodes must always be up, not sure if that is true or not but forms my problem……...

If you have two DC’s, and you have 3 nodes deployed, 1 in DC1 and 2 in DC2, what happens if DC2 goes down?

That would mean for redundant DC’s you would need to deploy 5 A3’s to make sure there is always two nodes active?

Appreciate any clarification.

Many thanks in advance

Re: Why A3 needs to be deployed in odd numbers and how to make resilient across two DC's

OscarK — Mon, 01 Feb 2021 15:38:34 GMT

Hi Martin, the odd number has to do with the election which A3 node will handle the authentication and an odd number is the recommended number.

Of course when one goes down the remaining 2 will fully operate but it is recommended to have an odd number as soon as possible.

/Oscar

Re: Why A3 needs to be deployed in odd numbers and how to make resilient across two DC's

Anonymous — Mon, 08 Feb 2021 05:00:04 GMT

Hi Oscar,

Thanks for posting an answer.

In refence to the comment below

“Of course when one goes down the remaining 2 will fully operate but it is recommended to have an odd number as soon as possible.”

Due to the odd numbering, and say you had three nodes, then essentially you could have two in one DC.

So my query is also, can it run on just one A3, if the DC with the 2 goes down?

My assumption is yes, but wanted to confirm?

Many thanks.

Re: Why A3 needs to be deployed in odd numbers and how to make resilient across two DC's

OscarK — Mon, 08 Feb 2021 20:50:46 GMT

Yes it can.