Question on route tables in Azure

anil kumar 1,641 Reputation points
2021-07-08T11:13:07.327+00:00

Hello,

I am new to Azure, pls don't get upset if I am doing/asking something silly.

In order to understand how user defined routing work in Azure, I have created below resources:

  • In my subscription
  • Virtual machine VM1 in Vnet1 and VM3 in Vnet3
  • Both Vnet1 and Vnet3 are peered so ping works between VM1 and VM3.
  • Also created one routing table
  • In another subscription where I have been granted Contributor Access
  • Virtual machine VM4 in Vnet4
  • No peering is configured to and from Vnet4 I want to route my connection from VM3 to VM1 - it should come via VM4. While creating a new route I have provided:
  • Address space of Vnet1 under Address prefix
  • Selected Virtual Appliance under Next hop type (I know I just have VM, not NPA as such, I hope it would work and I have enabled IP forwarding from NIC of VM4. )
  • Then provided the public IP of VM4 under next hop address (it's static and standard tier) and saved the changes.

Ran Tracert and found routing is not working as expected. I can some other option to select from while creating routes like virtual network and internet but I don't know how routing will work those options.

Pls help me understand how to make it work. Thank you!!

Azure Virtual Network
Azure Virtual Network
An Azure networking service that is used to provision private networks and optionally to connect to on-premises datacenters.
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Accepted answer
  1. GitaraniSharma-MSFT 48,016 Reputation points Microsoft Employee
    2021-07-12T08:12:43.843+00:00

    Hello @anil kumar ,

    Apologies for the delay in response.

    All your configuration looks fine except the NVA setup.

    While IP forwarding is an Azure setting, the virtual machine must also run an application able to forward the traffic, such as firewall, WAN optimization, and load balancing applications. The operating system of your VM must be able to forward network traffic and be configured to do so. To determine required settings within the virtual machine, see the documentation for your operating system or network application.
    Please refer:
    https://learn.microsoft.com/en-us/azure/virtual-network/virtual-networks-udr-overview#user-defined
    https://learn.microsoft.com/en-us/azure/virtual-network/virtual-network-network-interface#enable-or-disable-ip-forwarding
    https://learn.microsoft.com/en-us/azure/virtual-network/diagnose-network-routing-problem#considerations

    You need to turn on IP forwarding within the NVA VM OS following the steps mentioned in the below tutorial (this tutorial assumes you're using Windows Server 2019 Datacenter):
    https://learn.microsoft.com/en-us/azure/virtual-network/tutorial-create-route-table-portal#turn-on-ip-forwarding-within-myvmnva

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

    ----------------------------------------------------------------------------------------------------------------

    Please "Accept the answer" if the information helped you. This will help us and others in the community as well.


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