Exam Professional Cloud Network Engineer topic 1 question 13 discussion

D - Because you can't update the selectors after creating the VPN they need to be left open. This from GCP: When you create a route based tunnel using the Cloud Console, Classic VPN performs both of the following tasks: Sets the tunnel's local and remote traffic selectors to any IP address (0.0.0.0/0) For each range in Remote network IP ranges, Google Cloud creates a custom static route whose destination (prefix) is the range's CIDR, and whose next hop is the tunnel.

with route-based, you dont have to select local networks, only remote networks.. Answer should be B

D is the correct answer: Both policy-based and route-based VPNs in Google Cloud support IKEv2, but with some important distinctions. Policy-based VPNs allow for multiple CIDRs per traffic selector when using IKEv2, while route-based VPNs automatically use 0.0.0.0/0 as traffic selectors and rely on custom static routes. The key requirement is minimal overhead to scale in the future.

Policy-based VPNs require defining specific local and remote IP ranges (traffic selectors). When new subnets are added on either side, the VPN tunnel configuration (traffic selectors) must be updated, potentially requiring tunnel recreation, which increases overhead and potential downtime. Route-based VPNs typically use broad traffic selectors (like 0.0.0.0/0). Adding new subnets only requires updating the routes (static routes in this case), not the tunnel configuration itself. This significantly reduces operational overhead and minimizes downtime during network expansion.

A & B (Policy-Based VPNs): Google discourages policy-based VPNs because they require explicit selectors per subnet, leading to manual reconfiguration as the network grows. This increases operational overhead and downtime when adding new subnets. C (Route-Based VPN with Specific Traffic Selectors): Configuring specific traffic selectors instead of 0.0.0.0/0 makes the setup less flexible. If you add a new subnet, you need to update the traffic selectors, leading to downtime. Conclusion: D is the best option because it follows Google-recommended practices by using: ✅ Route-based VPN (flexibility, scalability). ✅ Traffic selectors set to 0.0.0.0/0 (simplifies route management). ✅ Static routes (since BGP is not supported on-prem).

Option B is the correct choice in this case, as it fits the scenario of connecting a non-BGP-capable on-premises VPN device to Google Cloud. Since the device doesn't support BGP (which is commonly used in route-based VPNs for dynamic routing), you cannot use route-based VPN that typically relies on dynamic routing protocols like BGP. Instead, Policy-based VPN is a better fit here, as it uses static traffic selectors to determine which traffic should be routed through the VPN tunnel. With Policy-based VPN, you can configure specific IP ranges (local and remote traffic selectors) to control the traffic flow. Additionally, you would set up static routes to ensure the traffic between your on-premises network and Google Cloud is correctly routed. This solution works well for non-BGP-capable devices, providing a straightforward method to connect to Google Cloud without the need for dynamic routing.

I'll go with D "operational overhead when your network grows"

The choice is between B & D. while D maybe ideal for growth purposes, we're talking about Google-recommended practices and setting 0.0.0.0/0 traffic selectors may have some unintended traffic flows

D - Because you can't update the traffic selectors after creating the VPN tunnel. When the network grows you have to destroy and create from scratch the tunnel

on-prem device doesn't support BGP

am going with A, gemini for B "it doesn't specify creating a tunnel per subnet, which is crucial for scalability and minimizing downtime"

-With route-based when using gcloud the local and remote selector are specified[1] -Also when using gcloud it is necessary to use commands to create the static routes[2] -It makes more sense selecting D, because that option will avoid having to modify the traffic selector when the network grows [1]https://cloud.google.com/network-connectivity/docs/vpn/how-to/creating-static-vpns#:~:text=To%20configure%20a%20route%2Dbased%20VPN%20tunnel%2C%20run%20the%20following%20command%3A [2]If you use the gcloud CLI to create the tunnel, you must use additional gcloud commands to create the routes

Choose B. Explanation: Cloud VPN Instance: You need to create a Cloud VPN instance to establish the VPN connection between your on-premises network and GCP. Policy-Based VPN Tunnel: In this option, a policy-based VPN tunnel is chosen. This approach uses traffic selectors to determine which traffic should be sent over the VPN tunnel. It is a valid option, especially when dealing with non-BGP-capable on-premises VPN devices that support only IKEv2. Local and Remote Traffic Selectors: Configure the local and remote traffic selectors to match your on-premises and GCP networks. This ensures that the correct traffic is allowed through the VPN tunnel. Static Routes: Configure the appropriate static routes to direct traffic through the VPN tunnel. This is essential for routing traffic between your on-premises network and GCP.

To minimise operational downtime for future network growth you need to preselect all possible addresses - i.e. option D

https://cloud.google.com/network-connectivity/docs/vpn/concepts/choosing-networks-routing

Final answer is B , only in policy based we can configure both remote and local ranges , and we can omit option A coz it cant be configured per subnet level

Cloud VPN disallows editing any traffic selectors after you have created a VPN. To change either the local or the remote traffic selector for a Cloud VPN tunnel, you must delete the tunnel and then re-create it. You do not have to delete the Cloud VPN gateway, though.