Question 1hardmultiple choice
Full question →hardmultiple choiceObjective-mapped
A company has a hub-spoke network topology. The hub virtual network contains an Azure Firewall and an ExpressRoute gateway for on-premises connectivity. The spoke virtual network hosts a critical application. They need to ensure that all outbound traffic from the spoke to the internet and to on-premises networks is routed through the Azure Firewall. They configure a user-defined route (UDR) on the spoke subnet with address prefix 0.0.0.0/0 and next hop as the Azure Firewall's private IP. They also disable 'Virtual network gateway route propagation' on the spoke subnet. However, traffic to on-premises still bypasses the firewall and goes through the ExpressRoute gateway. What is the most likely cause?
Answer choices
Why each option matters
Good practice is not just finding the correct option. The wrong answers often show the exact trap the exam wants you to fall into.
A
Distractor review
The Azure Firewall is not in the same region as the spoke.
Azure Firewall can be in a different region than the spoke VNet. Regional differences do not affect routing if the firewall is accessible via the hub VNet.
B
Distractor review
The ExpressRoute gateway's BGP routes are still overriding the UDR because gateway propagation is not fully disabled.
Disabling gateway route propagation removes learned routes from the subnet's effective routes. If properly disabled, BGP routes should not be present. This is not the cause.
C
Best answer
The spoke subnet does not have a route for the on-premises prefix pointing to the firewall.
The 0.0.0.0/0 UDR only applies to traffic with no more specific match. On-premises traffic has a specific address prefix. To route it through the firewall, you must add a UDR with that specific prefix and the next hop as the firewall.
D
Distractor review
The route table is not associated with the spoke subnet.
If the route table were not associated with the subnet, no UDR would apply at all, and traffic would use default routes. But internet traffic was being routed through the firewall, indicating the route table is associated.
Common exam trap
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Technical deep dive
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
- CIDR notation defines the prefix length.
- Block size helps identify subnet boundaries.
- Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
- The required host count determines the smallest suitable subnet.
TExam Day Tips
- Write the block size before choosing the subnet.
- Check whether the question asks for hosts, subnets or a specific address range.
- Do not confuse /24, /25, /26 and /27 host counts.
Related practice questions
Related AZ-500 practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
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Keep practising from the same exam bank, or move into a focused topic page if this question exposed a weak area.
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FAQ
Questions learners often ask
What does this AZ-500 question test?
CIDR notation defines the prefix length.
What is the correct answer to this question?
The correct answer is: The spoke subnet does not have a route for the on-premises prefix pointing to the firewall. — Disabling 'Virtual network gateway route propagation' prevents routes from the ExpressRoute gateway from being automatically added to the subnet's route table. However, the UDR with 0.0.0.0/0 only covers internet-bound traffic. Traffic destined to on-premises networks uses the specific prefix learned from ExpressRoute (e.g., 10.0.0.0/8). Even with propagation disabled, the route table does not have a route for that specific on-premises prefix. The 0.0.0.0/0 route is less specific, so traffic matching the on-premises prefix will not use it. To force on-premises traffic through the firewall, you must add an explicit UDR for the on-premises address prefix with next hop as the Azure Firewall. The Azure Firewall's location and route table association are not the issue here.
What should I do if I get this AZ-500 question wrong?
Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.
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