The answer is Internet, because Azure route selection uses the longest prefix match to determine the next hop. When a VM sends traffic to 172.16.1.20, Azure compares all available routes—both system routes and user-defined routes (UDRs)—and selects the route with the most specific prefix. Here, 172.16.1.0/24 is more specific than 172.16.0.0/16, so the Internet next hop wins over the virtual appliance, regardless of route priority or order. On the AZ-104 exam, this concept frequently appears in scenario-based questions where a broader route seems correct but a narrower UDR overrides it. A common trap is assuming the virtual appliance route takes precedence because it is a custom route, but prefix specificity always trumps route type. Remember: Azure routes by the longest prefix, not the lowest cost or highest priority. Memory tip: “More bits in the mask, more specific the task.”
AZ-104 Implement and Manage Virtual Networking Practice Question
This AZ-104 practice question tests your understanding of implement and manage virtual networking. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. A key principle to apply: azure routing uses the longest prefix match algorithm.. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A subnet has a route table with these user-defined routes: 172.16.0.0/16 -> Virtual appliance 10.1.1.4 and 172.16.1.0/24 -> Internet. A VM in the subnet sends traffic to 172.16.1.20. Which next hop is used?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Internet, because the most specific route prefix always wins.
Azure route selection uses the longest prefix match (most specific route) to determine the next hop. The route 172.16.1.0/24 is more specific than 172.16.0.0/16, so traffic to 172.16.1.20 uses the Internet next hop, not the virtual appliance. This is consistent with how Azure evaluates user-defined routes (UDRs) and system routes.
Key principle: Azure routing uses the longest prefix match algorithm.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Virtual appliance 10.1.1.4, because the broader route was added first.
Why it's wrong here
Route addition order does not matter when Azure selects the next hop for a destination.
✓
Internet, because the most specific route prefix always wins.
Why this is correct
Azure chooses the longest matching prefix. The /24 route is more specific than the /16 route.
Related concept
Azure routing uses the longest prefix match algorithm.
✗
Virtual network gateway, because all traffic to private IP addresses uses the gateway by default.
Why it's wrong here
A VPNgateway is not selected unless a matching route points to it or system routing requires it.
✗
No next hop, because conflicting user-defined routes disable routing for that destination.
Why it's wrong here
Conflicting routes are not disabled; Azure still uses the most specific valid route.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume route priority is based on the order routes are added (first match wins) rather than the longest prefix match, leading them to incorrectly choose the virtual appliance route.
Detailed technical explanation
How to think about this question
Azure routing uses a prefix-based longest prefix match algorithm, similar to how IP forwarding works in routers. The route table is evaluated in order of prefix length, not creation time; a /24 prefix always takes precedence over a /16 for overlapping destinations. In practice, this means you can create a default route (0.0.0.0/0) to a virtual appliance and still override specific subnets (e.g., 172.16.1.0/24) to force traffic out to the internet for inspection or bypass.
KKey Concepts to Remember
Azure routing uses the longest prefix match algorithm.
A /24 route is more specific than a /16 route for an overlapping IP.
User-defined routes (UDRs) override system routes when more specific.
Route creation order does not influence Azure's next hop selection.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Azure routing uses the longest prefix match algorithm.
Real-world example
How this comes up in practice
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this AZ-104 question in full detail.
Implement and Manage Virtual Networking — This question tests Implement and Manage Virtual Networking — Azure routing uses the longest prefix match algorithm..
What is the correct answer to this question?
The correct answer is: Internet, because the most specific route prefix always wins. — Azure route selection uses the longest prefix match (most specific route) to determine the next hop. The route 172.16.1.0/24 is more specific than 172.16.0.0/16, so traffic to 172.16.1.20 uses the Internet next hop, not the virtual appliance. This is consistent with how Azure evaluates user-defined routes (UDRs) and system routes.
What should I do if I get this AZ-104 question wrong?
Review azure routing uses the longest prefix match algorithm., then practise related AZ-104 questions on the same topic to reinforce the concept.
What is the key concept behind this question?
Azure routing uses the longest prefix match algorithm.
About these practice questions
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A subnet has a route table with these user-defined routes: 10.10.0.0/16 to Virtual appliance, 10.10.5.0/24 to Virtual network gateway, and 10.10.5.128/25 to Virtual network. The subnet is attached to a VM that sends traffic to several destinations. Which three next-hop decisions are correct? Select three.
hard
✓ A.Traffic to 10.10.5.9 uses Virtual network gateway.
✓ B.Traffic to 10.10.5.200 uses Virtual network.
✓ C.Traffic to 10.10.8.4 uses Virtual appliance.
D.Traffic to 10.10.5.9 uses Virtual appliance.
E.Traffic to 8.8.8.8 uses Virtual appliance.
Why A: Option A is correct because the route table uses longest prefix match. The destination 10.10.5.9 falls within the 10.10.5.0/24 range, which has a more specific prefix (24 bits) than 10.10.0.0/16 (16 bits). The user-defined route for 10.10.5.0/24 specifies a next hop of Virtual network gateway, so traffic to 10.10.5.9 is forwarded to the gateway.
Variation 2. A spoke subnet has a user-defined route for 10.60.0.0/16 that sends traffic to a virtual appliance at 10.1.0.4. The same subnet also learns a propagated route for 10.60.0.0/16 from a VPN gateway. A VM in the subnet sends traffic to 10.60.7.25. Which next hop will Azure use?
hard
✓ A.The virtual appliance at 10.1.0.4
B.The VPN gateway
C.The Internet
D.No next hop is available
Why A: Azure uses the most specific route match, and user-defined routes (UDRs) take precedence over propagated routes (BGP) for the same prefix. Since the UDR for 10.60.0.0/16 with next hop 10.1.0.4 is more specific than the propagated route from the VPN gateway, traffic to 10.60.7.25 is forwarded to the virtual appliance.
Last reviewed: Jun 11, 2026
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