Hello @Khushboo Kumari ,
Welcome to Microsoft Q&A Platform. Thank you for reaching out & hope you are doing well.
I understand that you want to setup an ExpressRoute connection for your on-premises and would like to know if it only connects one office to one connection at the same price, or you have to pay extra and can one ExpressRoute connection connect multiple on-premises.
ExpressRoute allows you to create a connection between your on-premises network and the Microsoft cloud in four different ways:
- CloudExchange Co-location
- Point-to-point Ethernet Connection
- Any-to-any (IPVPN) Connection
- ExpressRoute Direct
The CloudExchange Co-location, Point-to-point Ethernet Connection and ExpressRoute Direct are the connectivity models which would basically allow you to connect from a single on-premises office to Azure.
But Any-to-any (IPVPN) Connection allows you to integrate your WAN with the Microsoft cloud. IPVPN providers (typically MPLS VPN) offer any-to-any connectivity between your branch offices and datacenters. The Microsoft cloud can be interconnected to your WAN to make it appear like any other branch office.
So, you can choose Any-to-any (IPVPN) connectivity model when working with your connectivity provider to connect multiple on-premises at the same time.
So, as long as you have a WAN connectivity between your multiple on-premises, you can integrate Azure via ExpressRoute into the model and access it from any connected site.
To setup Azure ExpressRoute, please go through the below docs:
Routing requirements: https://learn.microsoft.com/en-us/azure/expressroute/expressroute-routing
You can go through the below article which provides architectural best practice for Azure ExpressRoute.
Kindly let us know if the above helps or you need further assistance on this issue.
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