Azure-docs: State that a subnet can only be associated with 1 app service

[DOMZE]

The statement "The new feature requires an unused subnet in your Resource Manager VNet." implies that the subnet can be associated to only 1 app service.

In fact when trying to associate the same vNet/subnet combination in the portal, the following error occurs
Subnet SUBNET_NAME in VNET VNET_NAME is already occupied by service /​s​u​b​s​c​r​i​p​t​i​o​n​s​/...​/​r​e​s​o​u​r​c​e​G​r​o​u​p​s​/​...​/​p​r​o​v​i​d​e​r​s​/​M​i​c​r​o​s​o​f​t​.​W​e​b​/​s​e​r​v​e​r​f​a​r​m​s​/AppServiceName

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Document Details

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• ID: a7a98803-1438-b1b5-f543-7dd88bc4294e
• Version Independent ID: 37ff1d0f-ed8e-5e4d-1f4c-1b9f6cffb938
• Content: Integrate app with Azure Virtual Network - Azure App Service
• Content Source: articles/app-service/web-sites-integrate-with-vnet.md
• Service: app-service
• GitHub Login: @ccompy
• Microsoft Alias: ccompy

[AidanTfL]

Hi everyone,

We are unable to add VNET integration to our new App Service and App Service plan, as the subnet is already occupied by a previous app service plan it was integrated with, that we've since deleted.

We've submitted a Support Request to Microsoft, but as the VNET Integration feature is still in preview, we're wondering if anyone else has experienced similar issues?

Additional steps we've taken so far:
1) We've even tried deleting the resource group the old app service and app service plan was in, but still have no success.

2) Next, we tried deleting the subnet with the intention of recreating it, then trying to add VNET integration to our app service again. However, we've had no success with deleting the subnet either, experiencing the same issue as described in November 2018, in this post:

https://social.msdn.microsoft.com/Forums/officeocs/en-US/6979fdac-e20b-4801-beb8-b09ce846ec54/unable-to-delete-vnet-or-subnet?forum=WAVirtualMachinesVirtualNetwork

[RyanHill-MSFT]

Thanks for the feedback! We are currently investigating and will update you shortly.

[RyanHill-MSFT]

@DOMZE, I went through steps outlined above. I created a vnet/subnet and was able to assign it to the app service. Now, a vnet I had configured with a gateway and associated public ip I was not able to assign to the app service due to the associated public ip. That is a separate issue which I don't believe addresses your question. If it does, please let me know. I also didn't run into any issues disconnecting one configured vnet and connecting a separate vnet to the app service using the Vnet integration preview blade. Could you elaborate further on how you configured your vnet/subnet? I want to replicate the same issue you ran into.

Regards,

Ryan

[DOMZE]

Hi @RyanHill-MSFT ,

Thanks for testing.

To actually reproduce the problem:
Create a vNet call it vNetTest with a subnet (/27) call it subnetA. Associate it to a web app call it webAppA
Create another app service plan with another web app call it webAppB

Try to associate vNetTest/subnetA to webAppB

You will get the error above

[RyanHill-MSFT]

Hi @DOMZE thanks for your provided steps. You can always use the Vnet Integration blade to disconnect application from the vnet and then reassoicate vnet to a different webapp. So I do believe the doc is correct. However, in the portal, you shouldn't be able to select the vnet if it's associated to an app service. I'll send this feedback to the appropiate team.

Thanks and regards,

Ryan

[DOMZE]

Hi @RyanHill-MSFT
yes what I meant by my statement is that once a subnet is associated to a web app, the subnet is thus associated to the app service it belongs to and you cannot add other web apps from other app services to it, thus it's a 1 to 1 association.

Thank you

[RyanHill-MSFT]

Thanks for the feedback! I have assigned the issue to the content author to investigate further and update the document as appropriate.

[RyanHill-MSFT]

@AidanTfL sorry for this inconvenience. I'll dig and see what I can find out.

[AidanTfL]

@AidanTfL sorry for this inconvenience. I'll dig and see what I can find out.

@AidanTfL Have you been able to reproduce this issue, or is it a specific issue with one of your Virtual Networks?
(Source: from the separate Issue I raised here:)
https://github.com/MicrosoftDocs/azure-docs/issues/29335

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I believe our issue occurred due to a bug in Azure, where the App Service and App Service Plan hadn't been 100% deleted. Everything was deleted other than the VNET reservation...

This issue is a known issue with the 'New VNET Integration (Preview)' feature to the App Service Engineering team.

By making a support request within the portal, we were able to get this fixed within our subscriptions.

If anyone has a similar issue, you can raise a support request via the Portal, if you have a support plan. Alternatively, email: [email protected] to be granted a one-time free Technical support request.

Note: please be advised only 1 App Service Plan can be attached to a subnet with new VNET Integration (Preview).

[psallis]

I think this is linked. I have created a subnet and connected an app without issue.
I've created a second subnet in the VNET and was able to associate to a second app plan. However, my app is unable to make a connection? Is there limitation on the number Apps Plans and Subnets per vnet?

[SamirFarhat]

Hi all,
Please clarify the statement so everyone can understand here this limitation:

• Can a Subnet (Not a Vnet)- be used by more than one Web App (App Service app) ?

[psallis]

Any update on having multiple App plans connecting to their own subnet within the vnet?
I get the following error when using tcpping.

Connection attempt failed: A socket operation encountered a dead network

[RyanHill-MSFT]

Let me see what I can find out @psallis

[psallis]

Hey @RyanHill-MSFT any luck?

[sbraunschweiger]

@RyanHill-MSFT, I currently have 2 App Services (each in separate App Service Plans) connected to a vnet gateway via P2S. I want to retire the gateway and connect via vnet integration subnet. Since only 1 App Service Plan can integrate with a vnet subnet, I was planning to create a second integration subnet (sn2) in the same vnet and associate the second App Service Plan with sn2. Has my intended configuration supported? Looks like @psallis had a problem with this.

[seanvelir]

Hi all,
Please clarify the statement so everyone can understand here this limitation:

• Can a Subnet (Not a Vnet)- be used by more than one Web App (App Service app) ?

In the documentation it states
"The integration subnet can only be used by only one App Service plan"

I don't understand why you would need a /27 subnet if you can only use a single webapp.

[sbraunschweiger]

https://docs.microsoft.com/en-us/azure/app-service/web-sites-integrate-with-vnet#regional-vnet-integration
The above article states the following ...

• When VNet Integration is used with VNets in the same region as your app, it requires the use of a delegated integration subnet with at least 32 addresses in it.
  
  
  
  • This feature is supported for Windows app production workloads with the following limitations:
    
    
    
    
    
    • The integration subnet can only be used by only one App Service Plan
    
    
    
  
  

Given the above constraints, I need 2 delegated integration subnets in my vnet because I have 2 App Services each in their own App Service Plan.

Controlled
From: Sean Dailey [e-mail]
Sent: Monday, July 15, 2019 3:28 PM
To: MicrosoftDocs/azure-docs [e-mail]
Cc: Steven C Braunschweiger [e-mail]; Comment [e-mail]
Subject: Re: [MicrosoftDocs/azure-docs] State that a subnet can only be associated with 1 app service (#29302)

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Hi all,
Please clarify the statement so everyone can understand here this limitation:

• Can a Subnet (Not a Vnet)- be used by more than one Web App (App Service app) ?

This is all I want to understand as well. I don't understand why you would need a /27 subnet if you can only use a single webapp.

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[jackiejaiau]

Basically we have the same issue.

Web App 1 connects to Subnet 1
Web App 2 connects to Subnet 2

Now everything OK. Then we disconnect both Web App to both subnet.

Web App 2 connects to Subnet 1
Web App 1 connects to Subnet 2

When the time web app 2 connects to subnet 1, it failed due to Subnet 1 is already occupied by a previous app service plan.

It may take few hours and few days to release the subnet 1.
I guess this is still preview that's why we have this issue?

[stefsch]

The docs have been updated previously to indicate: "The integration subnet can only be used by only one App Service plan" and "You can have only one regional VNet Integration per App Service plan. Multiple apps in the same App Service plan can use the same VNet."

[stefsch]

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