Azure Availability Set and Host Pool deployments

Pedro Duarte 26

Hi guys, does any one know why Azure doesn't assign a Public IP address during the deployment of a session host (VM) on a Host Pool when an Availability set is chosen?

Fails every time because there is no Internet connectivity so the Azure DSC extension fails to install and that causes the deployment to fail, if however I select no infrastructure redundancy is required the deployment completes and Azure assign a Public ip to my Session host (VM)

Thanks

Alan Kinane 16,786 Reputation points MVP

2021-11-18T11:43:01.183+00:00

Can I ask why you need public IP addresses for your session hosts? I will need to check this behaviour but generally you would not want to have public IP addresses on your session hosts so I am just wondering if there is a particular reason you require this?
Pedro Duarte 26 Reputation points

2021-11-18T11:52:32.637+00:00

Hi and thanks for your reply,

I need one to complete the deployment as stated above and this is a Host pool for remote working with (Application group) Microsoft remote desktop app.

During the configuration of the session host you are not given the option to have one but azure still give you one, it doesn't create it or anything just NAT the VM ipv4 address to a public address.

Once the deployment completes I then create a public IP and associate it to the nic.

Accepted answer

Alan Kinane 16,786 Reputation points MVP

2021-11-18T13:22:57.197+00:00

This is the same issue that I had and described in my post. If you remove the public IP address (or replace with a Basic SKU) on the existing VM then you should be OK.

If you need a static IP address for your hosts for MFA or whitelisting then the easiest option is to deploy a NAT gateway. This will NAT all outbound traffic on your subnet (or entire VNET if you want) through a single public IP address. I blogged about this also: https://azurealan.ie/2020/04/27/outbound-nat-for-azure-virtual-machines/

Here is the how to deploy guide: https://learn.microsoft.com/en-us/azure/virtual-network/nat-gateway/tutorial-create-nat-gateway-portal
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1 additional answer

Alan Kinane 16,786 Reputation points MVP

2021-11-18T12:09:50.63+00:00

Any VMs should NAT to the Internet automatically without the requirement of a public IP address. I have never had any issues deploying session hosts into availability sets. I would check first what DNS settings are configured for your virtual network? If you have custom DNS servers, are these reachable by your session hosts?

If that's all OK then can you give more details about the availability set. Is it a new Av Set or are there VMs in there already?
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Pedro Duarte 26 Reputation points

2021-11-18T12:17:37.78+00:00

Thank you,

That is the whole point, I'm using custom dns servers but the only thing that changes the deployment to fail is adding it to a an AV set.

I only have one VM running on that AV set and the deployment completed fine, it was the second vm that fails to complete.

thanks

Alan Kinane 16,786 Reputation points MVP

2021-11-18T12:43:30.323+00:00

Do you have an existing public IP address assigned to the VM already in the availability set and is it a Standard SKU or Basic SKU public IP address? I had some issues with this before and actually wrote up a post about it - https://azurealan.ie/2019/12/13/a-lesson-learned-on-outbound-connections-with-standard-sku/

I would recommend not having any public IP addresses on your session hosts at all. You don't need them and they just increase your security footprint. If you need to access the session hosts for whatever reason then you can RDP privately from another VM or use a service like Azure Bastion.

Pedro Duarte 26 Reputation points

2021-11-18T12:58:06.977+00:00

Thank you,

The first VM was deployed exactly like the second but the second fails.

I associated a Standard Public Ip address after the deployment completed and these vms are part of a host pool for people across the Country and World to work on.

Any Additional session hosts fail to complete the deployment if I go with the availability set where the first VM is already running.

As mentioned before seems like for whatever reason any additional session host deployments fail to complete if included on that AV set, and it took me some time to understand as it doesn't make much sense

VDI on Azure is the use of Azure resources and services to create an infrastructure for the remote delivery of desktops. ... The service is designed to enable you to deliver Windows desktops to your users on nearly any client device.

We already have one but it is the old one, this is the new SPRING VDI Environment

Just to add that they need a Static Public Ip address for MFA and other external services
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