PCNE Practice Exam 3 — 20 Questions

Question 1

A company wants to connect an on-premises network to Google Cloud using Cloud VPN. The on-premises network has a single subnet and no dynamic routing capabilities. The company needs a simple, low-cost solution. Which VPN configuration should they choose?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

Classic VPN with route-based configuration. Classic VPN with route-based configuration is the correct choice because the on-premises network lacks dynamic routing capabilities and requires a simple, low-cost solution. Route-based VPNs use static routes and do not require BGP, making them ideal for environments without dynamic routing support. Classic VPN is the legacy, lower-cost option compared to HA VPN, and route-based configuration allows traffic to be forwarded based on routing table entries rather than policy-based selectors.

Answer

HA VPN with dynamic routing (BGP)

Answer

HA VPN with static routing

Answer

Classic VPN with policy-based configuration

Question 2

A company uses Shared VPC. They want to restrict which service project's VMs can use a specific subnet. Which TWO methods can achieve this? (Choose TWO.)

Accepted Answer

Use IAM roles on the subnet resource to grant 'compute.subnetUser' to specific service projects.. IAM roles on a subnet resource allow you to grant the `compute.subnetUser` role to specific service projects, which controls which projects can create VM instances in that subnet. This is a direct method to restrict subnet usage within a Shared VPC environment, as the role grants permission to use the subnet without granting broader network access.

Answer

Use VPC network peering.

Answer

Use firewall rules to deny traffic from other service projects.

Answer

Use network tags on VMs and associate the subnet with those tags.

Question 3

Drag and drop the steps to configure a Cloud NAT for private instances to access the internet into the correct order.

Accepted Answer

Create a Cloud Router in the region, then create a Cloud NAT gateway using that router, then assign static IP addresses to the NAT, then apply the NAT to the desired subnets, then test connectivity from a private instance.. Cloud NAT requires a Cloud Router first. Then create NAT, assign IPs, and apply to subnets. Testing confirms internet access.

Answer

Create a Cloud NAT gateway first, then create a Cloud Router, then assign IP addresses, then apply to subnets, then test connectivity.

Answer

Create a Cloud Router, then assign IP addresses to the NAT, then create the Cloud NAT, then apply to subnets, then test.

Answer

Create a Cloud Router, then create a Cloud NAT and apply it to subnets, then assign IP addresses, then test connectivity.

Question 4

An engineer is troubleshooting a High Availability VPN setup. The VPN tunnels are established, but the BGP sessions are flapping. Which THREE factors could cause this? (Choose THREE.)

Accepted Answer

Mismatched BGP hold timer values. BGP session flapping can be caused by mismatched parameters, MTU issues, or authentication problems.

Answer

Incorrect VLAN ID on the VLAN attachment

Answer

Duplicate AS number on the on-premises router

Question 5

A company is using Network Connectivity Center (NCC) to connect multiple on-premises sites and GCP VPCs in a hub-and-spoke topology. Which TWO statements about NCC are correct?

Accepted Answer

NCC automatically propagates routes between all spokes.. NCC supports both VPC spokes and hybrid spokes (VPN/Interconnect). It does not support direct VPC-to-VPC peering; that's VPC peering. Route propagation is automatic within NCC.

Answer

NCC supports direct VPC-to-VPC peering without a hub.

Answer

NCC can only connect to on-premises networks via Dedicated Interconnect.

Answer

NCC requires all spokes to be in the same region.

Question 6

A company has deployed an HTTP load balancer with a backend service configured to use an unmanaged instance group. Users report that traffic is not reaching the backend instances. The backend instances are healthy and have proper firewall rules allowing traffic from the load balancer. What step should the network engineer take to resolve the issue?

Accepted Answer

Add a route for the load balancer's IP range.. The load balancer sends traffic to backend instances using their internal IP addresses. If there is no route from the load balancer's frontend IP range to the subnet containing the backend instances, traffic will be dropped. Adding a route for the load balancer's IP range ensures that packets can reach the instances. Since the problem states firewall rules are already proper, Option A (health check firewall rules) is unnecessary. Health checks are already configured (Option B is not needed). Instances do not require external IPs (Option C). Therefore, the correct step is to add the missing route.

Answer

Configure a firewall rule to allow health check probes from the load balancer's health check ranges.

Answer

Enable HTTP health check on the backend service.

Answer

Assign an external IP address to each backend instance.

Question 7

Drag and drop the steps to set up a Cloud Interconnect connection for dedicated on-premises connectivity into the correct order.

Accepted Answer

1. Order Cloud Interconnect, 2. Create VLAN attachment, 3. Complete cross-connect, 4. Configure BGP session, 5. Verify connectivity. Cloud Interconnect requires ordering, VLAN attachment, cross-connect, BGP, and verification.

Answer

1. Create VLAN attachment, 2. Order Cloud Interconnect, 3. Complete cross-connect, 4. Configure BGP session, 5. Verify connectivity

Answer

1. Order Cloud Interconnect, 2. Complete cross-connect, 3. Create VLAN attachment, 4. Configure BGP session, 5. Verify connectivity

Answer

1. Order Cloud Interconnect, 2. Configure BGP session, 3. Create VLAN attachment, 4. Complete cross-connect, 5. Verify connectivity

Question 8

A company has deployed an external HTTPS load balancer with a Cloud CDN backend. The load balancer uses a managed SSL certificate. Recently, the company updated their DNS record to point to a different IP address of a new load balancer. After the change, some users are still being served from the old load balancer's cache. The network engineer has confirmed that the DNS TTL has expired. What is the most likely cause of this issue?

Accepted Answer

Cloud CDN cached responses from the old load balancer may still be served until their cache TTL expires.. Cloud CDN caches content at Google's edge caches based on the cache-control headers or default cache TTL. When the DNS record is updated to point to a new load balancer, the old load balancer's cached responses may still be served from edge caches until their cache TTL expires, even after the DNS TTL has expired. This is because Cloud CDN caches are independent of DNS resolution and are governed by HTTP caching rules.

Answer

The old load balancer's SSL certificate is still cached by clients.

Answer

The DNS change has not propagated globally despite the TTL expiring.

Answer

The old load balancer's IP address is still being served by Google's edge network due to anycast.

Question 9

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. 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 10

A security engineer wants to allow SSH access to a VM that has no external IP. The VM is in a VPC with IAP configured. What is the simplest way to enable secure SSH without a bastion host?

Accepted Answer

Use Identity-Aware Proxy (IAP) TCP forwarding with the gcloud compute start-iap-tunnel command.. Identity-Aware Proxy (IAP) TCP forwarding allows secure SSH access to a VM without an external IP by tunneling traffic through the IAP service. The `gcloud compute start-iap-tunnel` command establishes an encrypted tunnel from your local machine to the VM via the IAP proxy, using the VM's internal IP and port 22. This eliminates the need for a bastion host or public IP while leveraging IAP's identity-based access controls.

Answer

Create a VPN tunnel to the VPC and SSH over the VPN.

Answer

Configure a SOCKS proxy on a bastion host.

Answer

Assign an external IP to the VM and use a firewall rule to restrict access.

Question 11

A company wants to enforce that all HTTPS load balancer traffic uses TLS 1.2 or higher. Which Google Cloud resource should they configure?

Accepted Answer

SSL policy attached to the target HTTPS proxy. An SSL policy in Google Cloud can be attached to a target HTTPS proxy to enforce minimum TLS version requirements, such as TLS 1.2 or higher. This policy directly controls the TLS handshake parameters at the load balancer level, ensuring that only clients supporting TLS 1.2 or above can establish HTTPS connections.

Answer

SSL certificate resource

Answer

VPC firewall rule to block TLS 1.0/1.1

Answer

Identity-Aware Proxy (IAP)

Question 12

A company has a VPC with subnets in us-east1 and us-west1. They have established a Cloud VPN tunnel to their on-premises network through a Cloud Router in us-east1. They want to ensure that traffic from on-premises to resources in us-west1 uses the VPN tunnel and not the public internet. What must be configured?

Accepted Answer

Add a route on the on-premises router for us-west1 subnets with next hop pointing to the VPN tunnel. The on-premises router must have a route for the us-west1 subnets with the VPN tunnel as the next hop. Without this, the on-premises router will use its default route (typically the public internet) to reach us-west1, bypassing the VPN tunnel. The Cloud Router in us-east1 advertises the us-west1 subnets via BGP over the VPN tunnel, but the on-premises router must be explicitly configured to forward traffic for those subnets into the tunnel.

Answer

Configure a custom dynamic route on the Cloud Router for us-west1 subnets

Answer

Create a separate VPN tunnel from on-premises to a Cloud Router in us-west1

Answer

Configure VPC firewall rules to allow traffic from on-premises to us-west1

Question 13

An organization wants to use Cloud DNS to forward DNS queries from on-premises to Google Cloud for a private zone. Which feature should they implement?

Accepted Answer

Inbound DNS policy. Inbound DNS policy provides a Google-managed forwarding IP address in your VPC that on-premises resolvers can use to forward queries to Cloud DNS private zones.

Answer

DNS peering

Answer

Outbound DNS forwarding zone

Answer

Private zone with DNS forwarding

Question 14

An organization wants to reduce egress costs for data sent from Compute Engine instances to users worldwide. Which TWO approaches should they consider? (Choose TWO.)

Accepted Answer

Deploy instances in multiple regions closer to users.. Cloud CDN caches content at edge locations, reducing egress from origin. Using a Premium Tier network routes traffic over Google's network, which may not reduce egress cost but improves performance; however, Standard Tier egress is cheaper than Premium Tier for internet egress. For reducing costs, Cloud CDN and using Standard Tier (if acceptable) can help. But among the options, Cloud CDN and placing instances in multiple regions (to serve users locally) reduce egress.

Answer

Enable Private Google Access to avoid internet egress for Google APIs.

Answer

Use global load balancers instead of regional load balancers.

Answer

Use Premium Tier networking to route traffic over Google's network.

Question 15

Which THREE of the following are valid use cases for VPC Service Controls?

Accepted Answer

Controlling access to a Cloud SQL database from a specific VPC.. VPC Service Controls allow you to define a service perimeter that restricts access to a Cloud SQL database (or other Google Cloud services) to requests originating from a specific VPC network. This is achieved by configuring an access level that references the VPC network, ensuring that only traffic from that VPC can reach the database, even if the database is exposed via private IP.

Answer

Allowing access to a managed instance group from the internet.

Answer

Enabling private access to Cloud APIs from on-premises.

Question 16

A company is experiencing asymmetric routing between their VPC and on-premises network over two Cloud VPN tunnels with different BGP sessions. Some traffic from GCP to on-premises is dropped by firewall stateful inspection on-premises. What is the most likely cause?

Accepted Answer

Traffic is taking one tunnel for outbound and the other for return, causing stateful firewall to drop packets.. The most likely cause is asymmetric routing, where outbound traffic from GCP to on-premises takes one VPN tunnel while return traffic takes the other. Stateful firewalls track connection state based on the first packet seen; if return packets arrive via a different tunnel (and thus a different source IP or interface), the firewall does not recognize them as part of an existing session and drops them. This is a classic symptom of asymmetric routing with multiple BGP sessions over separate tunnels.

Answer

BGP keepalive timers are set too low, causing session flapping.

Answer

The MTU is mismatched between the tunnels.

Answer

The on-premises router is not receiving the VPC routes via BGP.

Question 17

A company has a Dedicated Interconnect connection between their on-premises data center and Google Cloud. They are experiencing intermittent connectivity issues on a specific VLAN attachment. The VLAN attachment is configured with a single Cloud Router and BGP sessions are established. Which two steps should they take to troubleshoot the issue? (Choose two.)

Accepted Answer

Verify the BGP session status on the Cloud Router.. BGP session status on the Cloud Router directly indicates whether the routing protocol is functioning correctly between the on-premises router and Google Cloud. Intermittent connectivity on a VLAN attachment often stems from BGP flapping or session drops, which can be verified by checking the BGP state (e.g., Established, Idle, or Active) and associated error counters in the Google Cloud Console or via gcloud commands.

Answer

Check the MTU configuration on the on-premises router.

Answer

Verify the physical interconnect location and cable connections.

Answer

Review the Cloud NAT configuration for the VPC network.

Question 18

A company is migrating its on-premises infrastructure to Google Cloud. They need to connect their VPC to a third-party SaaS provider that only supports IPsec VPN. The company requires high availability and automatic failover. Which solution should they implement?

Accepted Answer

Deploy two Cloud VPN tunnels from two Cloud Routers with BGP sessions to the peer VPN device.. Deploying two Cloud VPN tunnels from two Cloud Routers with BGP sessions provides high availability and automatic failover. The two Cloud Routers in different zones ensure redundancy, and BGP (Border Gateway Protocol) dynamically advertises routes and detects tunnel failures, allowing traffic to automatically switch to the healthy tunnel without manual intervention. This meets the requirement for an IPsec VPN connection to a third-party SaaS provider that only supports IPsec VPN.

Answer

Use Dedicated Interconnect with VLAN attachments to the SaaS provider.

Answer

Deploy a Classic VPN tunnel with policy-based routing.

Answer

Deploy a single Cloud VPN tunnel and use static routing.

Question 19

A network engineer needs to create a firewall rule that blocks all ingress traffic from the internet to Compute Engine instances tagged 'web-server', except for traffic from the organization's VPN gateway at IP 203.0.113.1. The engineer creates a rule with priority 1000, deny ingress, source IP ranges 0.0.0.0/0, and targets 'web-server'. To allow the VPN IP, what should the engineer do?

Accepted Answer

Create a new allow rule with priority 500, source IP 203.0.113.1/32, target 'web-server', and action allow.. Firewall rules are evaluated in order of priority (lower number = higher priority). The deny rule at priority 1000 will deny all IPs. To allow the VPN IP, a higher priority (lower number) allow rule must be created for that specific IP, before the deny rule is evaluated. The correct approach is to create an allow rule with priority 100 (or any lower number) for source IP 203.0.0.0/8 (or the specific IP) targeting web-server.

Answer

Modify the existing deny rule to include an exception for the VPN IP in the source IP field.

Answer

Delete the deny rule and create a single rule that denies all IPs except the VPN IP using the 'except' option.

Answer

Change the priority of the existing deny rule to 1 and create an allow rule with priority 2 for the VPN IP.

Question 20

A company uses Cloud VPN tunnels to connect multiple sites to Google Cloud. They have a primary and a backup tunnel for redundancy, each with a different Cloud Router (both in the same region). BGP sessions are established on both routers. The network team notices that during a failover test, traffic fails over to the backup tunnel but then after 30 seconds, the backup tunnel traffic stops and does not recover until the primary tunnel comes back. The engineer finds that the backup Cloud Router is advertising the same routes as the primary, but the backup tunnel's BGP session shows that the routes are being withdrawn after 30 seconds. Additionally, the BGP session remains established. What is the most likely cause?

Accepted Answer

The backup Cloud Router's BGP session is experiencing a keepalive timeout due to incorrect timers.. The backup Cloud Router's BGP session remains established, but routes are withdrawn after 30 seconds. This is classic behavior of a BGP keepalive or hold timer mismatch: if the backup router expects a keepalive within a shorter interval than the peer sends, the hold timer expires, causing the router to withdraw all routes learned from that peer while keeping the TCP session alive (or re-establishing it). The 30-second interval matches the default BGP hold timer (90 seconds) divided by three, suggesting a timer misconfiguration on the backup router.

Answer

The backup Cloud Router is configured with a lower MED value, causing the routes to be withdrawn.

Answer

The backup tunnel is using a static routing method instead of dynamic BGP.

Answer

The backup tunnel's Cloud Router is in a different region, and the routes are not propagated globally.