PCNE Quick Quiz — 10 Questions

Question 1

An organization is migrating to Google Cloud and requires connectivity between their on-premises network and VPC. They plan to use Cloud VPN with dynamic routing (BGP). Which VPC feature is required for this setup?

Accepted Answer

Cloud Router. Cloud Router is required when using Cloud VPN with dynamic routing (BGP) because it manages the BGP sessions between the on-premises router and the Google Cloud VPN gateway. It exchanges routes dynamically, enabling automatic route propagation and failover without manual static route configuration.

Answer

Cloud NAT

Answer

VPC peering

Answer

VPC Flow Logs

Question 2

A company is migrating on-premises DNS to Google Cloud. They have a hybrid network using Cloud VPN and want to resolve on-premises hostnames from Compute Engine instances without custom scripts. Which service should they use?

Accepted Answer

Use Cloud DNS inbound server policy to forward queries to on-premises DNS.. Cloud DNS inbound server policy allows on-premises DNS servers to receive DNS queries from Compute Engine instances by creating a VPC-scoped policy that forwards queries to the IP addresses of on-premises DNS resolvers over Cloud VPN. This enables hybrid name resolution without custom scripts, as the policy automatically handles the forwarding of DNS requests from Google Cloud resources to the on-premises DNS infrastructure.

Answer

Create a forwarding zone in Cloud DNS and associate it with the VPC.

Answer

Enable Private Google Access on the VPC subnet.

Answer

Configure Cloud NAT to forward DNS queries to on-premises DNS servers.

Question 3

A network engineer is configuring a Cloud Router for BGP peering with an on-premises router over a VPN tunnel. The on-premises router uses 169.254.x.x link-local addresses. Which BGP peer IP should the engineer use in the Cloud Router configuration?

Accepted Answer

169.254.0.1. The correct BGP peer IP is 169.254.0.1 because Cloud Router uses the first IP in the 169.254.0.0/16 link-local range for BGP peering over a VPN tunnel. This is required by Google Cloud's implementation, where the on-premises router must use a link-local address from the 169.254.0.0/16 range, and Cloud Router automatically assigns 169.254.0.1 as its own BGP peer IP. The on-premises router typically uses 169.254.0.2 as its BGP peer IP, ensuring a point-to-point link-local BGP session.

Answer

10.0.0.1

Answer

The tunnel's external IP address

Answer

The on-premises router's external IP address

Question 4

A company uses Cloud NAT to allow private instances to reach the internet. They notice that egress traffic from Compute Engine VMs is intermittently failing. The VMs are in us-central1-a and use the default VPC network. Cloud NAT is configured with a single NAT IP address. What is the most likely cause?

Accepted Answer

Port exhaustion due to insufficient NAT IP addresses. Cloud NAT uses source network address translation (SNAT) to map private VM IPs to a public NAT IP. With only a single NAT IP address, the available port range (typically 64,512 ephemeral ports per NAT IP per VM) can be exhausted under high egress traffic, causing intermittent failures. This is the most likely cause given the symptom of intermittent failures and the single IP configuration.

Answer

Missing default route to Internet gateway

Answer

Cloud NAT not configured in the correct region

Answer

Firewall rule blocking egress traffic from VM

Question 5

Match each VPC networking concept to its definition.

Question 6

Drag and drop the steps to troubleshoot a VPN tunnel that is not passing traffic into the correct order.

Question 7

A company has a VPC with subnets in us-east1 and europe-west1. They have deployed a global external HTTP(S) load balancer with backend services in both regions. Users in Europe report high latency. What is the most likely cause?

Accepted Answer

Session affinity set to CLIENT_IP, causing sticky sessions to a distant backend. Option D is correct because CLIENT_IP session affinity causes the load balancer to hash the client's IP address to a specific backend instance. If a user in Europe is hashed to a backend in us-east1, all their requests will be forwarded to that distant region, resulting in high latency. This occurs even though a healthy backend exists in europe-west1, because the affinity overrides the load balancer's normal least-latency or proximity-based routing.

Answer

Incorrect health check configuration causing backends to be marked unhealthy

Answer

Firewall rules blocking traffic from the load balancer's health check probes

Answer

The load balancer is not enabled for global access

Question 8

A company uses an internal TCP/UDP load balancer to distribute traffic to a backend service. The backend instances are in an unmanaged instance group. Some instances fail health checks and are removed. What happens to existing connections to failed instances?

Accepted Answer

Existing connections are terminated immediately.. When an instance in an unmanaged instance group fails a health check, the internal TCP/UDP load balancer immediately terminates all existing connections to that instance. This is because the load balancer does not support connection draining for unmanaged instance groups; it simply stops forwarding new traffic and drops existing flows to the failed instance. The abrupt termination occurs because the load balancer operates at Layer 4 and has no mechanism to gracefully close TCP connections or wait for application-level cleanup.

Answer

The load balancer drains existing connections before removing the instance.

Answer

Existing connections are seamlessly redirected to healthy instances.

Answer

The load balancer waits for all existing connections to close before removing the instance.

Question 9

An organization has multiple VPCs in Google Cloud that need to communicate with an on-premises network through a single Dedicated Interconnect. All VPCs are in the same project. What is the most efficient way to enable connectivity from all VPCs to on-premises?

Accepted Answer

Create a Cloud Router per VPC, each with its own VLAN attachment on the same Interconnect. Option C is correct because each VPC requires its own Cloud Router and VLAN attachment to establish a dedicated BGP session over the same Dedicated Interconnect. This allows multiple VPCs in the same project to share a single physical interconnect while maintaining separate Layer 3 routing domains. A single VLAN attachment cannot be shared across VPCs, as each attachment is associated with exactly one Cloud Router and one VPC.

Answer

Create a separate Interconnect for each VPC

Answer

Create a single VLAN attachment and use it for all VPCs

Answer

Use VPC Network Peering to connect VPCs and attach one VPC to Interconnect

Question 10

A startup wants to create a VPC with a subnet that can grow automatically as they add more VM instances. Which subnet type should they use?

Accepted Answer

Auto mode subnet. An auto mode subnet automatically creates subnets in each region and assigns IP address ranges from a predefined pool that can expand as you add more VM instances. This allows the subnet to grow without manual intervention, making it ideal for startups that need dynamic scaling.

Answer

Custom mode subnet

Answer

Dynamic subnet

Answer

Legacy network