Google ACE Practice Question: Verify that a Compute Engine VM in `us-central1`…

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✗

  SSH into the VM and run `ping 10.1.2.3` to test connectivity.

  Why it's wrong here

  SSH into the VM and running `ping 10.1.2.3` tests whether ICMP echo requests reach the on-premises IP and whether replies return, but ICMP may be disabled by on-premises firewalls or by the VM’s own OS firewall even when TCP/UDP application traffic would succeed. Furthermore, a ping failure gives no information about which component is at fault: the VPC firewall, the Cloud VPN tunnel, the on-premises router, or the destination host's security settings. Connectivity Tests are more powerful because they simulate the exact protocol and port you care about (e.g., TCP 443) and trace every hop to reveal where the packet is dropped.

• ✓

  Use Network Intelligence Center Connectivity Tests to analyze the path from the VM to the on-premises IP.

  Why this is correct

  Connectivity Tests in Network Intelligence Center perform a simulated hop-by-hop analysis of a packet’s path from a VM to an on-premises IP, dynamically evaluating all applicable VPC firewall rules, routes, Cloud VPN tunnels, and Cloud Interconnect VLAN attachments. This allows the test to pinpoint the exact rule or route that is blocking traffic, such as an egress firewall rule denying traffic to the on-premises CIDR or a missing BGP route advertisement. Unlike simple reachability checks, Connectivity Tests do not require actual traffic or agent installations, making them safe and non-invasive for production troubleshooting.

• ✗

  Review Cloud VPN tunnel metrics in Cloud Monitoring for packet loss.

  Why it's wrong here

  The Cloud VPN tunnel metrics in Cloud Monitoring, such as `sent_packets`, `received_packets`, and `tunnel_status`, indicate whether the tunnel is up and whether data is flowing over it. However, these metrics provide only aggregate tunnel health and do not tell you whether traffic to a specific on-premises IP (10.1.2.3) is routed correctly, whether BGP is advertising the exact prefix, or whether firewall rules on either side permit the packet. A tunnel can appear healthy with no packet loss while still failing to deliver traffic to the intended destination due to misconfigured routes, overlapping CIDRs, or policy-based routing gaps.

• ✗

  Run `gcloud compute routes list` to verify the route to 10.1.2.3 exists.

  Why it's wrong here

  Running `gcloud compute routes list` only shows the static and dynamically learned routes that exist in your VPC network, and it confirms whether a route to 10.1.2.3 is present. However, the command does not validate that the route is actually being used by the VM, nor does it inspect the on-premises side of the connection—such as VPN gateway policies, BGP peer status, or on-premises firewall rules. A route can exist in the route table and still be ineffective because the next hop is unhealthy, the tunnel is down, or a firewall rule blocks the traffic before it reaches the route.

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