Routes and routing in GCP - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding GCP Route Priorities

You have two routes in Google Cloud Platform (GCP) with the same destination range but different priorities. Route A has priority 1000 and Route B has priority 500. Which route will GCP use to send traffic to that destination?

A Route B because it has a lower priority number.

B Route A because it was created first.

C Route A because it has a higher priority number.

D GCP will load balance traffic evenly between Route A and Route B.

💡 Hint

In GCP routing, lower priority numbers mean higher priority.

GCP uses the route with the lowest priority number to send traffic. So Route B with priority 500 is preferred over Route A with priority 1000.

❓ Configuration

intermediate

Configuring a Custom Static Route in GCP

You want to create a static route in GCP that directs traffic destined for 10.0.0.0/16 to a specific VM instance acting as a gateway. Which next hop type should you specify in the route configuration?

A Next hop IP address

B Next hop VPN tunnel

C Next hop instance

D Next hop internet gateway

💡 Hint

The next hop should be the VM instance acting as the gateway.

To route traffic through a specific VM instance, you specify the next hop as that instance in the route configuration.

❓ Architecture

advanced

Designing a Multi-Region Network with Custom Routes

You have two VPC networks in different regions connected via VPC peering. You want to ensure that traffic from region A to region B uses a specific firewall VM in region A as a gateway before reaching region B. Which routing approach achieves this?

A Create a custom static route in region A VPC with next hop instance set to the firewall VM and destination range of region B's subnet.

B Set up a VPN tunnel between the two regions and route traffic through it.

C Use dynamic routing with Cloud Router to automatically route traffic through the firewall VM.

D Use default routes and rely on VPC peering to handle traffic automatically.

💡 Hint

Custom static routes can direct traffic through specific instances.

By creating a custom static route with the firewall VM as next hop, traffic to region B is forced through the firewall VM in region A.

❓ security

advanced

Impact of Routes on Firewall Security in GCP

You have a firewall rule allowing traffic from subnet A to subnet B. However, traffic is still blocked. You discover a route that sends subnet B traffic through a different gateway that blocks the traffic. What is the best way to fix this routing issue to allow traffic flow?

A Disable the firewall rule and rely on routes to control traffic.

B Increase the priority of the firewall rule to override the route.

C Delete the conflicting route that sends traffic through the blocking gateway.

D Create a new route with a lower priority number that directs traffic through the correct gateway.

💡 Hint

Routes with lower priority numbers take precedence.

Creating a new route with a higher priority (lower number) that directs traffic through the correct gateway ensures traffic flows as intended without deleting existing routes.

❓ service_behavior

expert

Behavior of GCP Routes with Overlapping Destination Ranges

You have two routes in GCP with overlapping destination IP ranges: Route X with destination 10.0.0.0/16 and priority 1000, and Route Y with destination 10.0.0.0/24 and priority 1100. A VM sends traffic to IP 10.0.0.50. Which route will GCP use and why?

A Route X because it has a lower priority number.

B Route Y because it has a more specific destination range.

C Route X because it was created first.

D Route Y because it has a higher priority number.

💡 Hint

GCP prefers the most specific route regardless of priority.

GCP selects the route with the most specific destination range (longest prefix match) first, then uses priority if there is a tie. Here, 10.0.0.0/24 is more specific than 10.0.0.0/16, so Route Y is used.

Practice

1. What is the main purpose of a route in Google Cloud Platform networking?

easy

A. To create virtual machines

B. To store data in the cloud

C. To direct network traffic from one place to another

D. To monitor network usage

Solution

1. Step 1: Understand what routes do in networking

   Routes tell network traffic where to go, like a map for data packets.

2. Step 2: Identify the correct purpose in GCP context

   In GCP, routes guide traffic between subnets, VMs, and external networks.

3. Final Answer:

   To direct network traffic from one place to another -> Option C

4. Quick Check:

   Routes guide traffic = C [OK]

Hint: Routes always guide traffic flow in networks [OK]

Common Mistakes:

• Confusing routes with storage or compute services
• Thinking routes monitor traffic instead of directing it
• Mixing routes with firewall rules

2. Which of the following is the correct way to specify a next hop in a GCP route configuration?

easy

A. nextHopAddress: "192.168.1.1"

B. nextHop: "192.168.1.1"

C. nextHopGateway: "192.168.1.1"

D. nextHopIp: "192.168.1.1"

Solution

1. Step 1: Recall GCP route next hop syntax

   GCP routes use specific fields like nextHopIp to define the next hop IP address.

2. Step 2: Match the correct field name

   Among options, only nextHopIp is valid for specifying an IP address as next hop.

3. Final Answer:

   nextHopIp: "192.168.1.1" -> Option D

4. Quick Check:

   Correct field for IP next hop = nextHopIp [OK]

Hint: Use nextHopIp to specify IP address next hop [OK]

Common Mistakes:

• Using incorrect field names like nextHop or nextHopAddress
• Confusing next hop IP with gateway name
• Omitting quotes around IP address

3. Given the following route configuration snippet in GCP, what destination IP range will this route apply to?

{"destRange": "10.0.0.0/16", "nextHopIp": "192.168.1.1"}

medium

A. All IP addresses in 10.0.0.0 to 10.0.255.255

B. Only the IP 10.0.0.0

C. All IP addresses in 192.168.1.0/24

D. All IP addresses in 0.0.0.0/0

Solution

1. Step 1: Understand CIDR notation 10.0.0.0/16

   The /16 means the first 16 bits are fixed, covering IPs from 10.0.0.0 to 10.0.255.255.

2. Step 2: Identify the destination range

   The destRange field defines the IP range this route applies to, which is 10.0.0.0/16 here.

3. Final Answer:

   All IP addresses in 10.0.0.0 to 10.0.255.255 -> Option A

4. Quick Check:

   10.0.0.0/16 covers 10.0.0.0-10.0.255.255 [OK]

Hint: CIDR /16 covers 65,536 IPs starting at base address [OK]

Common Mistakes:

• Thinking /16 means only one IP
• Confusing nextHopIp with destination range
• Assuming 0.0.0.0/0 means local subnet

4. You created a route with destination range 0.0.0.0/0 but forgot to specify a next hop. What will happen when you try to deploy this route?

medium

A. The route will fail to create due to missing next hop

B. The route will be created and direct traffic to the internet automatically

C. The route will create but traffic will be dropped silently

D. The route will create and send traffic to the default gateway

Solution

1. Step 1: Recall route requirements in GCP

   Every route must have a destination and a next hop to know where to send traffic.

2. Step 2: Understand deployment validation

   Without a next hop, GCP rejects the route creation because it cannot route traffic properly.

3. Final Answer:

   The route will fail to create due to missing next hop -> Option A

4. Quick Check:

   Missing next hop causes creation failure [OK]

Hint: Routes need next hop or gateway to deploy [OK]

Common Mistakes:

• Assuming route auto-assigns next hop
• Thinking route silently drops traffic
• Confusing route creation with firewall rules

5. You want to route all traffic destined for 10.1.0.0/24 subnet through a VM instance with IP 192.168.5.10. Which route configuration is correct?

hard

A. {"destRange": "192.168.5.10/24", "nextHopIp": "10.1.0.0"}

B. {"destRange": "10.1.0.0/24", "nextHopIp": "192.168.5.10"}

C. {"destRange": "10.1.0.0/24", "nextHopGateway": "192.168.5.10"}

D. {"destRange": "0.0.0.0/0", "nextHopIp": "10.1.0.0"}

Solution

1. Step 1: Identify destination subnet to route

   The destination subnet is 10.1.0.0/24, so destRange must be this value.

2. Step 2: Specify next hop as VM IP

   The next hop should be the VM's IP 192.168.5.10, using nextHopIp field.

3. Step 3: Validate correct JSON structure

   {"destRange": "10.1.0.0/24", "nextHopIp": "192.168.5.10"} correctly sets destRange and nextHopIp with proper values and syntax.

4. Final Answer:

   {"destRange": "10.1.0.0/24", "nextHopIp": "192.168.5.10"} -> Option B

5. Quick Check:

   Destination subnet + VM IP next hop = {"destRange": "10.1.0.0/24", "nextHopIp": "192.168.5.10"} [OK]

Hint: Destination subnet in destRange, VM IP in nextHopIp [OK]

Common Mistakes:

• Swapping destination and next hop IPs
• Using nextHopGateway instead of nextHopIp for VM IP
• Setting wrong destination range