Professional-Cloud-Network-Engineer Exam Dumps : Google Cloud Certified - Professional Cloud Network Engineer

The problem description indicates that VMs in VPC2 receive traffic but their replies don't reach VPC1, especially when a VPN gateway fails. This strongly suggests an asymmetric routing issue, where VPC2's routing table might not be aware of all necessary routes to send return traffic to VPC1, particularly in a multi-region setup with failover. By default, VPC networks are in regional dynamic routing mode, meaning they only learn routes from Cloud Routers in the same region. To ensure that routes learned from one region (where the active VPN tunnel might be) are available globally across the VPC, you need to enable global dynamic routing mode in the VPC that is experiencing the return traffic issue (VPC2 in this case). This allows VPC2 to learn and apply routes from Cloud Routers in all regions, ensuring that even if a VPN tunnel fails in one region, the routes learned from the active tunnel in another region are still available for return traffic.

Exact Extract:

"A VPC network's dynamic routing mode controls whether routes learned by Cloud Routers in one region are available to VMs in other regions. By default, VPC networks are in regional dynamic routing mode, which means Cloud Routers in a region only advertise routes to and learn routes from other Cloud Routers in the same region. This can lead to asymmetric routing issues in multi-region deployments."

"To ensure that routes learned from Cloud Routers are propagated to all regions within a VPC network, you must set the dynamic routing mode to global."Reference: Google Cloud VPC Documentation - Dynamic routing mode

This answer meets the requirement of configuring one connection as Active for both ingress and egress traffic, and enabling automatic failover to the passive connection in case of failure. The reason is:

The advertised route priority is a value that Cloud Router uses to set the route priority when advertising routes to your on-premises router. The lower the value, the higher the priority1. By setting the advertised route priority as 200 for the active connection, you ensure that it has a higher priority than the passive connection, which has the default value of 1001. This way, your on-premises router will prefer the routes from the active connection over the passive one for ingress traffic.

The MED (Multi-Exit Discriminator) is a value that your on-premises router uses to indicate its preference for receiving traffic from Cloud Router. The lower the value, the higher the preference2. By advertising a lower MED on the active connection from your on-premises router, you ensure that Cloud Router will prefer sending traffic to the active connection over the passive one for egress traffic.

If the active connection fails, Cloud Router will stop receiving routes from it and will start using the routes from the passive connection for egress traffic. Similarly, your on-premises router will stop receiving routes with priority 200 from the active connection and will start using the routes with priority 100 from the passive connection for ingress traffic. This achieves automatic failover without any manual intervention.

Option A is incorrect because setting the advertised route priority > 10,200 on the active connection would deprioritize it globally in your VPC network, which is not what you want1. Option B is incorrect because advertising a lower MED on the passive connection would make Cloud Router prefer sending traffic to it over the active one, which is not what you want2. Option D is incorrect because setting the advertised route priority as 200 for both connections would make them equally preferred by your on-premises router, which is not what you want1.