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Difficulty: EasyConfigure User-Defined Routes and Routing Tables

An administrator is designing a virtual network routing solution. A virtual network contains two subnets named `SubnetA` and `SubnetB`. A firewall virtual machine named `NVA1` is deployed in `SubnetB`. The administrator wants to route all outbound internet traffic from the virtual machines in `SubnetA` through `NVA1` for inspection before it reaches the internet.

Which two actions must the administrator perform to achieve this goal?

  1. Create a route table containing a route with the destination `0.0.0.0/0` and next hop type of Virtual appliance pointing to the private IP address of `NVA1`, and associate the route table with `SubnetA`.Answer
  2. Enable IP forwarding on the network interface (NIC) of the `NVA1` virtual machine.Answer
  3. C
    Create a route table containing a route with the destination `0.0.0.0/0` and next hop type of Virtual network gateway pointing to the public IP address of `NVA1`, and associate the route table with `SubnetA`.
  4. D
    Enable IP forwarding on the network interfaces (NICs) of all virtual machines deployed in `SubnetA`.

Answer

To route internet-bound traffic from SubnetA through a network virtual appliance (NVA) in SubnetB, the administrator must create a route table with a default route (0.0.0.0/0) where the next hop type is set to Virtual appliance and the next hop IP address is the private IP address of NVA1. This route table must be associated with SubnetA. Additionally, the administrator must enable IP forwarding on the network interface (NIC) of NVA1 to allow it to forward traffic destined for other locations.
To route SubnetA's internet traffic through NVA1, a route table must be created with a route for 0.0.0.0/0 pointing to the private IP of NVA1 as a Virtual appliance next hop type, and this route table must be associated with SubnetA. In addition, the NVA's network interface must have IP forwarding enabled so Azure allows it to receive and process traffic destined for other IP addresses.

Step-by-Step Solution

1
Define the user-defined route (UDR) for internet-bound traffic.
A route with address prefix 0.0.0.0/0 is configured with a next hop type of Virtual appliance and the next hop IP address set to the private IP address of NVA1.
This tells Azure to override the default system route for internet traffic and direct it to the NVA.
2
Associate the route table with SubnetA.
The route table is applied to SubnetA.
The UDR is only applied to VMs within subnets associated with the route table.
3
Enable IP forwarding on the NVA's network interface.
IP forwarding is enabled in Azure for the NIC of NVA1.
By default, Azure drops traffic sent to a VM that is not destined for that VM's IP address. Enabling IP forwarding allows the NVA to receive and forward transit traffic.

Key Concept

Configuring custom routing through a Network Virtual Appliance (NVA) using route tables and IP forwarding.
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Topics

Configure User-Defined Routes and Routing Tables