PCNE Implementing Hybrid Interconnectivity — Timed 10 Questions

Question 1

A company is planning to migrate workloads to Google Cloud and needs to establish hybrid connectivity with high bandwidth (10 Gbps) and low latency. They also require the ability to scale bandwidth up to 80 Gbps in the future. Which TWO options should they consider?

10 minute time limit — choose an answer to begin.

Accepted Answer

Dedicated Interconnect. Dedicated Interconnect provides direct, private physical connections between your on-premises network and Google Cloud, supporting 10 Gbps or 100 Gbps per circuit. This meets the requirement for high bandwidth (10 Gbps) and low latency, and allows scaling up to 80 Gbps by adding multiple 10 Gbps circuits or using a 100 Gbps circuit. Partner Interconnect also provides private connectivity, but through a supported service provider, with options ranging from 50 Mbps to 10 Gbps per connection. Both Dedicated and Partner Interconnect can be used to achieve the required bandwidth and latency, and both can scale (Partner Interconnect by aggregating multiple connections). The other options (CDN Interconnect, Direct Peering, Cloud VPN) do not provide the guaranteed bandwidth, low latency, and scalability required.

Answer

CDN Interconnect

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Direct Peering

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Cloud VPN with multiple tunnels

Question 2

You are configuring a Cloud Router for a Dedicated Interconnect VLAN attachment. The on-premises BGP AS number is 65001. You want to ensure that traffic from Google Cloud to on-premises prefers the primary attachment over the backup. Which BGP attribute should you configure on the primary Cloud Router to achieve this?

Accepted Answer

Local preference. To influence traffic from Google Cloud to on-premises (outbound from GCP), you need to affect the path selection on the Cloud Router for received routes. Local preference is a well-known BGP attribute used to prefer one path over another when multiple paths are received to the same destination. By setting a higher local preference on the primary Cloud Router for routes received from the primary attachment, the Cloud Router will prefer that path for outbound traffic. MED influences inbound traffic to the advertiser (on-prem to GCP), not outbound from GCP.

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MED (metric)

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AS path prepending

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Weight attribute

Question 3

A company is deploying a Dedicated Interconnect with a 10 Gbps circuit to Google Cloud. They need to ensure high availability. Which configuration is required by Google Cloud to meet the high availability SLA?

Accepted Answer

Provision two VLAN attachments on two separate Cloud Routers in different zones. To meet the high availability SLA for Dedicated Interconnect, Google Cloud requires at least two VLAN attachments, each on a separate Cloud Router in different zones. This ensures that if one zone or Cloud Router fails, traffic can still flow through the other attachment, providing redundancy. A single VLAN attachment or a single Cloud Router does not meet the 99.99% availability SLA because it creates a single point of failure.

Answer

Combine Dedicated Interconnect with a Cloud VPN tunnel for failover

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Use Partner Interconnect instead of Dedicated Interconnect

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Provision a single VLAN attachment on one Cloud Router

Question 4

A company has a Hybrid Connectivity setup using Cloud VPN with dynamic routing (BGP). They notice that traffic from their on-premises network to Google Cloud is intermittently dropping. The on-premises BGP speaker is sending routes with a higher local preference (200) than the Google Cloud router (default 100). What is the most likely cause of the intermittent drops?

Accepted Answer

Asymmetric routing is causing traffic to be dropped by stateful firewalls. The on-premises BGP speaker is sending routes with a higher local preference (200) than the default on Cloud Router (100). This makes the on-premises route preferred for return traffic from Google Cloud, but the forward traffic from on-premises may still use the Cloud VPN tunnel. This asymmetry causes stateful firewalls (e.g., on-premises firewall or Google Cloud firewall) to drop packets that do not match an existing session, leading to intermittent drops.

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AS path prepending is causing route flapping

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Cloud Router is not configured for ECMP

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The BGP MED attribute is misconfigured

Question 5

A multinational corporation is connecting five on-premises data centers to Google Cloud using Cloud Interconnect. Each data center has a dedicated 10 Gbps connection. They want to ensure that if one Interconnect fails, traffic is automatically redistributed across the remaining connections without manual intervention. Which solution meets this requirement?

Accepted Answer

Use a Cloud Router with BGP and establish multiple BGP sessions over each Interconnect. Cloud Router with BGP enables dynamic routing, allowing multiple BGP sessions over each Cloud Interconnect. When one interconnect fails, BGP withdraws the affected routes, and traffic is automatically redistributed across the remaining BGP sessions without manual intervention. This meets the requirement for automatic failover and load balancing across the five 10 Gbps connections.

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Configure multiple VLAN attachments on a single Cloud Router and rely on link aggregation

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Deploy Cloud VPN tunnels as backup and configure static routes with lower priority

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Configure VPC Network Peering between all data centers and Google Cloud

Question 6

An organization wants to migrate legacy on-premises applications to Google Cloud but must maintain low-latency connectivity for real-time data synchronization. The on-premises data center is in a colocation facility that is not directly served by Google Cloud. Which hybrid connectivity option is most cost-effective while meeting the latency requirement?

Accepted Answer

Partner Interconnect. Partner Interconnect is the most cost-effective option because it provides a dedicated, low-latency connection through a supported service provider that can extend connectivity from the colocation facility to a Google Cloud region. Unlike Dedicated Interconnect, it does not require physical cross-connects in a Google Cloud colocation facility, making it ideal when the on-premises site is not directly served by Google Cloud. It meets the real-time synchronization latency requirement by offering a reliable, high-bandwidth connection with SLA-backed uptime.

Answer

Direct Peering

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Cloud VPN with dynamic routing

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Dedicated Interconnect

Question 7

A company is using Cloud VPN with BGP to connect their on-premises network to Google Cloud. They have two VPN tunnels from two different on-premises VPN gateways to a single Cloud VPN gateway. They notice that during maintenance on one on-premises gateway, traffic fails over to the other tunnel, but after the maintenance, traffic does not fail back. What is the most likely cause?

Accepted Answer

The BGP local preference on the primary tunnel is not higher than the backup tunnel. B is correct because BGP local preference is used to influence outbound traffic path selection. If the primary tunnel's local preference is not higher than the backup tunnel, BGP will not prefer the primary route after the backup session recovers, causing traffic to remain on the backup tunnel. This is a classic BGP route selection behavior where the highest local preference wins.

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Only one VPN tunnel can be active at a time

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Cloud VPN gateway does not support BGP

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The backup tunnel does not have a valid BGP session

Question 8

A financial services company is required to encrypt all data in transit between their on-premises data center and Google Cloud. They have a Dedicated Interconnect connection. They want to meet the encryption requirement while minimizing overhead and complexity. Which solution should they implement?

Accepted Answer

Enable MACsec on the Dedicated Interconnect. MACsec (IEEE 802.1AE) provides Layer 2 encryption on the Dedicated Interconnect link itself, encrypting all traffic between the on-premises router and the Google Cloud edge router without requiring any changes to applications or additional VPN gateways. This meets the encryption requirement with minimal overhead and complexity because MACsec operates transparently at the data link layer, adding negligible latency and no per-packet processing overhead compared to IPsec or TLS.

Answer

Enable TLS encryption on all applications

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Use Cloud VPN over the internet instead of Dedicated Interconnect

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Establish an IPsec VPN tunnel over the Dedicated Interconnect

Question 9

A company wants to connect their VPC to an on-premises network using Cloud VPN. They need to ensure that traffic from Google Cloud to on-premises uses a specific route only when the primary path is available, and otherwise fails over to a backup path. Which configuration should they use?

Accepted Answer

Configure BGP on Cloud Router and advertise custom routes with appropriate metrics. Cloud VPN with dynamic routing (BGP) allows you to control path selection by advertising custom routes with different metrics (MED values) for the primary and backup paths. When the primary path is available, the lower metric route is preferred; if the BGP session fails, the route is withdrawn and traffic automatically fails over to the backup path with a higher metric. This meets the requirement for active/passive failover without manual intervention.

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Configure Cloud NAT to route traffic through the backup path

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Use static routes with a higher priority for the primary path

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Create firewall rules to allow failover traffic

Question 10

An enterprise is using a 10 Gbps Dedicated Interconnect between their on-premises data center and Google Cloud. They measure throughput and find it is only 5 Gbps even though there is no congestion. The on-premises router is configured with a single VLAN attachment. What is the most likely cause?

Accepted Answer

The on-premises router does not support full line rate. A single VLAN attachment on a 10 Gbps Dedicated Interconnect means the on-premises router must handle all traffic through one physical interface. If the router lacks the forwarding capacity to process packets at 10 Gbps line rate, throughput will be capped at its maximum switching or routing performance, which in this case is 5 Gbps. This is a common hardware limitation, not a configuration or congestion issue.

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BGP is not configured, causing routing loop

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MTU mismatch between on-premises and Google Cloud

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QoS policy is limiting throughput on Google Cloud side