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  • Route propagation

  • alexsandro-ramos

    September 24, 2021 at 7:38 pm


    I have a doubt about question below.

    The company’s on-premises network has an established AWS Direct Connect connection to its VPC in AWS. A Network Engineer is designing the network infrastructure of a multitier application hosted in an Auto Scaling group of EC2 instances. The application will be accessed by the employees from the on-premises network as well as from the public Internet. The network configuration must automatically update routes in your route table based on your dynamic BGP route advertisement. What should the Engineer do to implement this network setup?

    The correct answer was: Enable route propagation in the route table of the VPC and add a
    specific route to the on-premises network. Specify the virtual private
    gateway as the target.

    My doubt is… If I enable route propagation, why I need do add a static route?

    I mean… the VGW is responsible for routing to on-primese through direct connect or vpn site-to-site… Ok? If I have a route propagation enabled, the subnet route table will have a route received from VGW destined for my on-premises network.. so in this case a static route is unnecessary.

    Could you clarify this question for me?

    Thank you!

  • Carlo-TutorialsDojo

    September 25, 2021 at 2:22 am

    Hello alex,

    Thank you for bringing this item to our attention.

    Yes, the routing between the VPC and on-premises network should be done at the VGW level when setting up the DX connection. Hence, you only need to specify the VGW as the target when enabling the route propagation. We will revise the option for this item.

    Let me know if you have further questions.


    Carlo @ Tutorials Dojo

    • KOKOKO

      December 16, 2023 at 10:53 pm

      Hi Carlo,

      Correct answer: Enable route propagation in the route table of the VPC and specify the virtual private gateway as the target.

      Here is my idea.
      It looks like not enough. EC2 can communicate on-premises network, but cannot communicate the internet because it doesn’t have (default) route for the internet. VPC with EC2 needs to have default route targeting IGW as well as propagated router by virtual private gateway.

      • This reply was modified 5 months, 2 weeks ago by  KOKOKO.
  • alexsandro-ramos

    September 25, 2021 at 2:48 am

    Hello Carlo,

    Thank you!

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