Expressroute bidirectionial?

Question

Hello
Is ER bidirectional?
We are reasearching the hub-spoke model and will be using private peering.
In the spoke network there will be a vm. We would like to let the vm connect with a on premise sql database. Would that be possible?

Greetings
Kick

Answer 1

Hello @C.J. Vieleers ,

Welcome to Microsoft Q&A Platform. Thank you for reaching out & hope you are doing well.

As mentioned in this doc, the private peering domain is considered to be a trusted extension of your core network into Microsoft Azure. You can set up bi-directional connectivity between your core network and Azure virtual networks (VNets).
https://learn.microsoft.com/en-us/azure/expressroute/expressroute-circuit-peerings#privatepeering

Yes, it is possible for the spoke VM to connect with an on premise sql database using ExpressRoute gateway. It can be achieved by the following 2 ways:

1) You can set Vnet peering between the spoke Vnet and Hub Vnet (where ExpressRoute gateway is deployed) and enable Gateway transit feature on the Vnet peering for the spoke Vnet to use the remote gateway for communication with the on-premises.
The ExpressRoute gateway will advertise the Address Space(s) of the Azure VNet to your on-premises. Also, if VNet Peering is used and the peered VNet has "Use Remote Gateway" enabled, the Address Space of the peered VNet will also be advertised.
Refer : https://learn.microsoft.com/en-us/azure/virtual-network/virtual-network-peering-overview#service-chaining
https://learn.microsoft.com/en-us/azure/virtual-network/virtual-network-peering-overview#pricing
https://learn.microsoft.com/en-us/azure/expressroute/expressroute-faqs#how-are-vnets-advertised-on-expressroute-private-peering

2) You can link the spoke Vnet to the ExpressRoute gateway directly for communication between the spoke Vnet and on-premises.
You can link up to 10 virtual networks on a standard ExpressRoute circuit, and up to 100 on a premium ExpressRoute circuit.
Refer : https://learn.microsoft.com/en-us/azure/expressroute/expressroute-howto-linkvnet-portal-resource-manager
https://learn.microsoft.com/en-us/azure/expressroute/expressroute-faqs#can-i-link-to-more-than-one-virtual-network-to-an-expressroute-circuit

Kindly let us know if the above helps or you need further assistance on this issue.

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