You manage an Azure subscription that contains a virtual network named `VNet-Corp` (172.16… — Microsoft Azure Administrator (AZ-104)

You manage an Azure subscription that contains a virtual network named `VNet-Corp` ( $172.16.0.0/12$ ). `VNet-Corp` contains three subnets:
- `Subnet-Web` ( $172.16.1.0/24$ )
- `Subnet-DB` ( $172.16.2.0/24$ )
- `Subnet-Sec` ( $172.16.100.0/24$ ) containing a Network Virtual Appliance (NVA) at IP address $172.16.100.10$ .

A route table named `RT-Web` is associated with `Subnet-Web`. `RT-Web` contains the following user-defined routes (UDRs):
- A route for destination $172.16.0.0/16$ with a next hop type of Virtual Network Gateway.
- A route for destination $172.16.2.0/24$ with a next hop type of Virtual appliance and a next hop IP address of $172.16.100.10$ .

IP forwarding is enabled on the network interface of the NVA. The default system route for the virtual network is $172.16.0.0/12$ with a next hop type of Virtual network.

A virtual machine in `Subnet-Web` attempts to send traffic to a database server at IP address $172.16.2.100$ in `Subnet-DB`.

Which next hop will Azure select for this traffic?

A
The Virtual Network Gateway because user-defined routes configured with a Virtual Network Gateway take precedence over Virtual Appliance routes.
The Network Virtual Appliance (NVA) at $172.16.100.10$ because the user-defined route for $172.16.2.0/24$ is the longest prefix match.Cevap
C
The Virtual network (default system route) because default system routes cannot be overridden by user-defined routes for destinations within the same virtual network.
D
The database server directly because local subnet routes always override user-defined routes.

Cevap

The Network Virtual Appliance (NVA) at

172.16.100.10

because the user-defined route for

172.16.2.0/24

is the longest prefix match.

When Azure routes traffic, it selects a route based on the Longest Prefix Match (LPM) algorithm among all matching routes (system routes and user-defined routes). The destination IP address

172.16.2.100

matches three routes: the system route (

172.16.0.0/12

), the UDR to the gateway (

172.16.0.0/16

), and the UDR to the NVA (

172.16.2.0/24

). Since

172.16.2.0/24

has the longest prefix (24 bits), Azure selects this route. Because this route is a user-defined route (UDR) and has a next hop type of Virtual appliance pointing to

172.16.100.10

, the traffic is forwarded to the NVA.

Adım Adım Çözüm

Identify all matching prefixes for the destination IP

172.16.2.100

The matching routes are: the default system route

172.16.0.0/12

, the UDR

172.16.0.0/16

, and the UDR

172.16.2.0/24

Before forwarding traffic, Azure evaluates all active routes in the subnet's effective route table to find matching destinations.

Compare the prefix lengths of the matching routes.

The prefix lengths are /12 (system route), /16 (gateway UDR), and /24 (NVA UDR).

Azure uses the Longest Prefix Match (LPM) algorithm to determine route precedence.

Select the route with the longest prefix and verify its next hop configuration.

The route

172.16.2.0/24

is selected, which directs traffic to the Virtual Appliance at

172.16.100.10

Since /24 is the longest and most specific prefix, it takes precedence over the /16 and /12 prefixes, overriding both the default system route and the gateway route.

Anahtar Kavram

Azure route selection precedence based on Longest Prefix Match (LPM) and User-Defined Route (UDR) overrides.

Tahmini Süre:1m 15s

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