Markus's Techzone

Markus's Techzone

Azure VNet Peering

Azure VNet Peering

Table of Contents

1 Current project situation
2 Hub and Spoke network
3 VNet Peering
4 Lab
4.1 Lab Topology
4.2 Lab VNet
4.2.1 Lab VNet Peering
4.3 Lab Functions
4.3.1 Lab Functions - VNet
4.3.2 Functions - Access Restrictions
4.4 Lab API Management
4.4.1 Lab API Management - VNet
4.5 Lab Data Flow and Requests
4.5.1 VM Cloud to On-Premise-Function
4.5.2 VM On-Premise to On-Premise-Function
4.5.3 VM Cloud to Cloud-Function
4.5.4 VM On-Premise to Cloud-Function
5 Code and Deployment
6 Further information

1 Current project situation

Our current project contains about 20 Azure Functions Apps in Premium Plan. These Functions Apps are connected with an Express Route to the On-Premise network and use a VNET subnet which is part of the On-Premise network.

This setup has a few drawbacks:

  • Based on the permissions, network changes can only be done by the company network group and not by the project group.
  • Because it's the same network, subnets and IP addresses are limited
  • Azure Function Apps running in a Premium Plan can scale out to 100 instances. Which means up to 100 IPs will be required for running the Azure Function Apps.

2 Hub and Spoke network

Hub and Spoke network Implement a hub-spoke network topology on Azure

The hub is a virtual network in Azure that acts as a central point of connectivity to your on-premises network. The spokes are virtual networks that peer with the hub, and can be used to isolate workloads. Traffic flows between the on-premises datacenter and the hub through an ExpressRoute or VPN gateway connection.

Hub and Spoke network Hub-spoke network topology in Azure

3 VNet Peering

With VNet Peering, Azure Virtual Networks can be connected:

Azure supports the following types of peering:

  • Virtual network peering: Connect virtual networks within the same Azure region.
  • Global virtual network peering: Connecting virtual networks across Azure regions.

4 Lab

For evaluation purpose, a lab has to be created with the following resources:

  • Azure Function Apps
  • Azure API Management
  • VNets
  • VMs
    • for connection testing

All resources are deployed in the same region.

The lab simulates a Hub and Spoke network. HTTP-Requests are made from VMs to test the data flow.

peering-azure-resources.png

4.1 Lab Topology

The lab consists of two VNets:

  • vnet-cloud
    • 172.16.0.0/16
    • Spoke
  • vnet-on-premise
    • 10.0.0.0/8
    • Hub and simulates the On-Premise-Network
      • simpler setup

API Management provides HTTP-Endpoints which forwards the requests to the Functions.

peering-azure-topology.png

4.2 Lab VNet

vnet-cloud with three subnets:

  • snet-vnet-cloud-backends
    • 172.16.64.0/19
    • for VM for making Http-requests
  • snet-vnet-cloud-apim
    • 172.16.252.0/22
    • for API Management
  • snet-vnet-cloud-resources
    • 172.16.32.0/19
    • for Azure Function App

peering-vnet-cloud-subnet.png

vnet-on-premise with two subnets:

  • snet-vnet-on-premise-backends
    • 10.96.0.0/11
    • for VM for making Http-requests
  • snet-vnet-on-premise
    • 10.128.0.0/9
    • for Azure Function App which represents a on-premise system

peering-vnet-onpremise-subnet.png

4.2.1 Lab VNet Peering

Both VNet Peerings are created with an ARM Template in the same subscription. Please check the How-To Guide if you want to create VNet Peering in different Subscriptions or with different deployment models.

peering-vnet-cloud-peering.png

peering-vnet-on-premise-peering.png

4.3 Lab Functions

Azure Functions networking options

VNet Integration depends on use of a dedicated subnet. When you provision a subnet, the Azure subnet loses 5 IPs for from the start.

Two Azure Functions Apps with HttpTrigger are deployed in the different VNets:

Function func-on-premise in VNET vnet-on-premise simualtes a On-Premise-System with Http-Endpoint.

4.3.1 Lab Functions - VNet

At least the Azure Function Premium Plan has to be used to configure Functions Apps with VNet integration.

peering-func-cloud-vnet.png

The storage accounts are also part of the (VNet)[docs.microsoft.com/en-us/azure/storage/comm..:

peering-storageaccount-cloud-vnet.png

4.3.2 Functions - Access Restrictions

Following Access Restrictions are configured for the Function App to allow only requests from API Management:

peering-function-cloud-accessrestrictions.png

So, the Function App can only be accessed from Subnet snet-vnet-cloud-apim 172.16.252.0/22.

peering-function-cloud-forbidden-shell.png

peering-function-cloud-forbidden-shell-vm-oncloud.png

peering-function-cloud-forbidden-shell-vm-onpremise.png

4.4 Lab API Management

API Management has one API with two operations which forwards the requests to the Azure Function Apps:

peering-apim-apis.png

Policies:

/evaluation/cloud

cloud-function: func-cloud.azurewebsites.net/api

    <inbound>
        <base />
        <set-backend-service base-url="{{cloud-function}}" />
        <rewrite-uri template="/CloudTrigger" copy-unmatched-params="true" />
    </inbound>

/evaluation/onpremise:

on-premise-function: func-on-premise.azurewebsites.net/api

    <inbound>
        <base />
        <set-backend-service base-url="{{on-premise-function}}" />
        <rewrite-uri template="/OnPremiseTrigger" copy-unmatched-params="true" />
    </inbound>

4.4.1 Lab API Management - VNet

API Management is part of the VNet subnet snet-vnet-cloud-apim and deployed as an internal VNet.

peering-apim-vnet.png

4.5 Lab Data Flow and Requests

4.5.1 VM Cloud to On-Premise-Function

A request from the Cloud-VNet to API Management forwards the request to the Function in the On-Premise-VNet:

peering-cloud-onpremise-mermaid-diagram-20210102172827.png

Mermaid

curl https://apim-eval-peering.azure-api.net/evaluation/onpremise

peering-curl-cloud-on-premise.png

4.5.2 VM On-Premise to On-Premise-Function

A request from the On-Premise-VNet to API Management forwards the request to the Function in the On-Premise-VNet:

peering-onpremise-onpremise-mermaid-diagram-20210102172344.png

Mermaid

curl https://apim-eval-peering.azure-api.net/evaluation/onpremise

peering-curl-on-premise-on-premise.png

4.5.3 VM Cloud to Cloud-Function

A request from the Cloud-VNet to API Management forwards the request to the Function in the Cloud-VNet:

peering-cloud-cloud-mermaid-diagram-20210102180822.png Mermaid

curl https://apim-eval-peering.azure-api.net/evaluation/cloud

peering-curl-cloud-cloud.png

4.5.4 VM On-Premise to Cloud-Function

A request from the On-Premise-VNet to API Management forwards the request to the Function in the Cloud-VNet:

peering-onpremise-cloud-mermaid-diagram-20210102180117.png Mermaid

curl https://apim-eval-peering.azure-api.net/evaluation/cloud

peering-curl-on-premise-cloud.png

5 Code and Deployment

The entire code can be found in GitHub.

All the resources (Azure resources, Function Apps, VMs) can be deployed with a script:

bash deploy.sh

Deploy only Azure resources:

Deploy To Azure Visualize

6 Further information

Choosing between Azure VNet Peering and VNet Gateways

  • VNet peering - connecting VNets within the same Azure region
  • Global VNet peering - connecting VNets across Azure regions

Enable containers to use Azure Virtual Network capabilities

 
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