CODEWITHSUNDEEP
azureroutesazure-virtual-networkvnet
Sayantan Ghosh
Sayantan Ghosh

Reputation: 1056

Routing traffic between VNets in Azure

If two vnets are connected to each other via multiple set of peering vnets, how does azure route the traffic? Fo example, lets consider the below: A, B, C, D are 5 VNets and the they are peered (bi-directionally with traffic forwarding allowed).

enter image description here

Now if A wants to send a packet to D, how it is determined whether it will take the A-B-C-D path or the A-E-D path?

Any docs will be helpful.

Upvotes: 2

Views: 12651

Answers (3)

Kaspatoo
Kaspatoo

Reputation: 1363

Some years ago but i think service chaining allows that as far as i understand the documentation

To enable service chaining, configure user-defined routes that point to virtual machines in peered virtual networks as the next hop IP address. User-defined routes could also point to virtual network gateways to enable service chaining.

Upvotes: 0

Nancy Xiong
Nancy Xiong

Reputation: 28224

As far as I know, VNet Peering connections are non-transitive. It seems that it's still on the roadmap. See the feedback here.

From your picture, If only VNet Peering connections between them, then A could not reach D, also A could not reach C. A only could reach direct-connected B and E.

If you want to allow much VNets communication. You could implement a hub-spoke network topology in Azure. As the hub network, you could deploy a VPN gateway then enable allow gateway transit to other spoke VNets and enable use remote gateways in each spoke VNets. If you require connectivity between spokes, consider implementing an NVA for routing in the hub, and using UDR(custom routes) in the spoke to forward traffic to the hub. In this scenario, you must configure the peering connections to allow forwarded traffic.

VNet Peering enables you to connect VNets through the Azure backbone network. Azure automatically creates a route table for each subnet within an Azure VNet and adds system default routes to the table. You can also override some of Azure's system routes with custom routes.

If multiple routes contain the same address prefix, Azure selects the route type, based on the following priority:

  • User-defined

  • route BGP route

  • System route

You could get more details about Virtual network traffic routing

Upvotes: 4

4c74356b41
4c74356b41

Reputation: 72171

According to this article you'd need an NVA somewhere, vnet peering is non transitive.

At the beggining of the same article they talk a bit more about this.

To sum it up. packet wont reach D from A unless you fix your networking setup

Upvotes: 1

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