Azure VM Scale Set - custom VM Names

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Azure VM Scale Set - custom VM Names

Kirubakara Senthil Kumar S 191

In the Azure VM ScaleSet i am running a Vendor product, This vendor product requires a fixed IP and host names to enable the listener at specific port. We deployed this VMSS in a subnet. By this way, we got the fixed IP. But, we are unable to get the fixed VM Names.

Any idea to get fixed VM Names for the VMs in the VMSS ??

I am looking fixed IP and Fixed host name. As we have fixed IP from Subnet, I would like to assign a Fixed name to the VM based on a IP. For example if the IP is 10.200.10.5 - I would like to assign the VM name as USXXXXX05.. something like this.

Kirubakara Senthil Kumar S 191 Reputation points

2022-02-24T04:33:26.013+00:00

This application is currently hosted On-Prem, there are four servers under a LB. So here, the IP and host names are fixed. They have configured it as expected by the vendor product. We are trying to migrate this to azure VMSS and we land in this issue. Please advise, if any of you have any idea to fix this issue.

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Kirubakara Senthil Kumar S 191 Reputation points

2022-02-24T04:33:26.013+00:00

This application is currently hosted On-Prem, there are four servers under a LB. So here, the IP and host names are fixed. They have configured it as expected by the vendor product. We are trying to migrate this to azure VMSS and we land in this issue. Please advise, if any of you have any idea to fix this issue.

Answer 1

shiva patpi 13,366 Microsoft Employee Moderator

Hello @Kirubakara Senthil Kumar S ,
It might not be possible to generate a custom VM Names when you deploy your machines in a Virtual Machine Scale Set.
By default all the VM names under VMSS takes a naming convention of : "{scale-set-name}_{instance-id}

Each VM in a scale set also gets a computer name assigned to it. This computer name is the hostname of the VM in the Azure-provided DNS name resolution within the virtual network. This computer name is of the form "{computer-name-prefix}{base-36-instance-id}".

The {base-36-instance-id} is in base 36 and is always six digits in length. If the base 36 representation of the number takes fewer than six digits, the {base-36-instance-id} is padded with zeros to make it six digits in length. For example, an instance with {computer-name-prefix} "nsgvmss" and instance ID 85 will have computer name "nsgvmss00002D".

For example if you use the below command to create VMSS:

az vmss create -g vmsstest -n vmsstest --computer-name-prefix comp --image UbuntuLTS

Then it will create a VMSS with 2 VMs
VM names will be vmsstest1 , vmsstest2
Computer Names will be comp1, comp2

For your scenario , If you still have a requirement of fixed host names - then you can try creating Standard VMs with your custom naming convention grouping in an AvailabilitySet and put those VMs behind a Load Balancer.

Please reference below documents:
(While creating the VMs you can customize the VM names based upon your above mentioned requirements)

https://learn.microsoft.com/en-us/azure/virtual-machines/windows/tutorial-availability-sets
https://learn.microsoft.com/en-us/azure/load-balancer/tutorial-multi-availability-sets-portal

Kirubakara Senthil Kumar S 191 Reputation points

2022-02-24T11:50:56.033+00:00

Thanks @shiva patpi for your detailed explanation.

The VMs doesn't have to follow a fixed naming convention. I am fine with whatever the pattern VM scale set is following.

Is there a possibility of getting the same name again for a VM in the VMSS.. It is creating new VM names every time.

Let me explain. Lets assume, Based on the load today VMSS, spins 3 VMs - ips are 10.xx.xx.4, 10.xx.xx.5, 10.xx.xx.6 and the host names for these VMs are nsgvmss00002D, nsgvmss00003D and nsgvmss00004D.

At the end of the day, it scales down to 1 VM. Next day when it scales up again - can i get a same VM names again for those same ips ?? Here IP remains the same.

Vendor Product requires a fixed VM IP and Hostname to be listed in its DB in order to start a service and enable the listener.

Other alternative, I am thinking is - is there a possibility to trigger a job/azure function, which can update the VM names directly to the DB, when a new VM spins up in VMSS ? VMSS has any capability to trigger a function/custom code ?

thanks in advance for your response.
Kirubakara Senthil Kumar S 191 Reputation points

2022-02-24T12:00:32.233+00:00

I believe, running a custom code at VM level is possible? Anyways the VMSS is running with a custom image to deploy the VMs. In the custom image, we can create a Script to update the DB with its IP and hostname and set it to run at the start of the machine? Hope this possible ? please share your feedback..
Kirubakara Senthil Kumar S 191 Reputation points

2022-02-24T12:23:22.233+00:00

Can VMSS, just shutdown the VMs instead of de-allocating it ? If this is possible, I can spin up all possible VMs in the subnet, capture all the names and shut down those VMs for the VMSS to start it. It might ruin the purpose of VMSS ?? All VMs will be charged?
Kirubakara Senthil Kumar S 191 Reputation points

2022-02-24T12:32:00.03+00:00

VMSS has any DNS clean up option?, if not, everytime when VMSS creates a new VM / VM name, the list will grow exponentially for every scale-up event??
shiva patpi 13,366 Reputation points Microsoft Employee Moderator

2022-03-08T00:57:43.377+00:00

When you Scale down the VMSS and scale up again - it can't retain the VMNames but it can retain the IPs and the IPs will be in an ascending & sequential order
the VM names numbers will be incremented by a numerical number
shiva patpi 13,366 Reputation points Microsoft Employee Moderator

2022-03-08T00:59:09.64+00:00

You can have an automation scription to STOP the VMs under the VMSS - Once you stop the VMs under VMSS and you won't be charged - Once you start the VMs you can retain the same Names & Same IPs

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Azure VM Scale Set - custom VM Names

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