Your company has an Azure virtual network named `VNet-Production` (10.10.0.0/16) that cont… — Microsoft Azure Administrator (AZ-104)

Your company has an Azure virtual network named `VNet-Production` ( $10.10.0.0/16$ ) that contains the following subnets:

* `FrontendSubnet` ( $10.10.10.0/24$ )
* `SecureAppSubnet` ( $10.10.20.0/24$ )
* `DMZSubnet` ( $10.10.99.0/24$ )

A Network Virtual Appliance (NVA) is deployed in `DMZSubnet` and has an IP address of $10.10.99.4$ .

A route table is associated with `FrontendSubnet` and contains the following route:

* Route name: `To-NVA`
* Destination IP address/CIDR: $10.10.20.0/24$
* Next hop type: `Virtual appliance`
* Next hop IP address: $10.10.99.4$

A user attempts to send traffic from a virtual machine in `FrontendSubnet` to a database server at $10.10.20.55$ in `SecureAppSubnet`.

Which two statements correctly describe how Azure routes this traffic based on prefix match and UDR override rules? (Select TWO.)

Azure will select the route with the destination prefix $10.10.20.0/24$ for traffic destined to $10.10.20.55$ because it is the longest prefix match (LPM).Answer
The user-defined route for $10.10.20.0/24$ overrides the default system VNet local route for that subnet range because user-defined routes take precedence over system routes.Answer
C
Azure will route the traffic using the default system local VNet route for $10.10.0.0/16$ because system routes always take precedence over user-defined routes.
D
Azure will discard the traffic because next-hop IP addresses for virtual appliances must be in the destination subnet rather than a transit subnet.

Answer

Azure will route the traffic using the user-defined route with the destination prefix

10.10.20.0/24

because it is the longest prefix match for

10.10.20.55

, and user-defined routes override the default system local virtual network routes.

Azure uses the Longest Prefix Match (LPM) algorithm to choose the route for a packet. Because the target IP address is

10.10.20.55

, the route for

10.10.20.0/24

is a longer prefix match than the default system route of

10.10.0.0/16

. Furthermore, User-Defined Routes take precedence over default system routes, ensuring the packet is correctly sent to the NVA rather than routed locally.

Step-by-Step Solution

Identify the destination IP and matching prefixes.

The target IP is

10.10.20.55

. The matching routes are the VNet local system route (

10.10.0.0/16

) and the user-defined route (

10.10.20.0/24

This establishes the candidates for routing evaluation.

Apply the Longest Prefix Match (LPM) rule.

The prefix

10.10.20.0/24

is longer and more specific than

10.10.0.0/16

LPM is the primary rule Azure uses to determine route selection among overlapping prefixes.

Evaluate UDR versus system route precedence.

The UDR (

10.10.20.0/24

) takes precedence over the default VNet local system route.

UDRs allow administrators to override system routes to redirect traffic (e.g., through an NVA).

Key Concept

Azure routes traffic based on the longest prefix match (LPM) first, and when prefixes match, User-Defined Routes (UDRs) override system routes.

Question

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

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