Update subnet of App Gateway V1

Question

Hi,

Can I extend/ shrink subnet of my V1 Application Gateway.

Thanks in advance!

Answer 1

Hi,

The subnet size is determined when you initially create the Application Gateway, and it's based on the subnet configuration you specify during the creation process.

If you need to change the subnet size you need to move to different subnet.

Please Note:

If subnet is named "GatewaySubnet" its reserved for VPN gateways. The Application Gateway V1 resources using the "GatewaySubnet" subnet need to be moved to a different subnet or migrated to V2 SKU before September 30, 2023 to avoid control plane failures and platform inconsistencies. For changing the subnet of an existing Application gateway, see steps https://learn.microsoft.com/en-us/azure/application-gateway/application-gateway-faq#can-i-change-the-virtual-network-or-subnet-for-an-existing-application-gateway

Please click "Accept as Answer" if this helps.

Answer 2

Hi,

You can create a new subnet in your existing VNET or you can add a new address space to your existing VNET and create a subnet for Application Gateway. Then you can use the below mentioned PowerShell script to move the Application gateway to the other subnet. Once moved, you can delete the existing subnet and shrink/expand as you needed and repeat the same process again to bring it back to the shrunk/expanded subnet.

Reference: https://learn.microsoft.com/en-us/azure/application-gateway/application-gateway-faq#can-i-change-the-virtual-network-or-subnet-for-an-existing-application-gateway

Regards,

Karthik Srinivas