You need to recommend a load balancing solution that meets the availability requirements.
Which load balancing solution should you recommend?
A . a Layer-7 load balancer with a single namespace and without session affinity
B . a Network Load Balancing (NLB) cluster
C . DNS round robin
D . a Layer-4 load balancer with multiple namespaces and without session affinity
Answer: A
Explanation:
From Scenario:
Contoso identifies the following high-availability requirements for the planned deployment: The network load balancer must be able to probe the health of each workload.
Load balancers that work on the Layer 7 of OSI model are intelligent. Layer 7 load balancer is aware of the type of traffic passing through it. This type of load balancer can inspect the content of the traffic between the clients and the Exchange server. From this inspection, it gets that results and uses this information to make its forwarding decisions. For example, it can route traffic based on the virtual directory to which a client is trying to connect, such as /owa, /ecp or /mapi and it can use a different routing logic, depending on the URL the client is connecting to. When using a Layer 7 load balancer, you can also leverage the capabilities of Exchange Server 2016 Managed Availability feature. This built-in feature of Exchange monitors the critical components and services of Exchange server and based on results it can take actions.
Note: Layer 7 load balancer can use this to detect functionality of critical services, and based on that information decide if it will forward client connections to that node. If the load balancer health check receives a 200 status response from health check web page, then the service or protocol is up and running. If the load balancer receives a 403 status code, then it means that Managed Availability has marked that protocol instance down on the Mailbox server.
Although it might look that load balancer actually performs a simple health check against the server nodes in the pool, health check web page provides an information about workload’s health by taking into account multiple internal health check probes performed by Managed Availability.
Incorrect Answers:
D: Load balancers that work on Layer 4 are not aware of the actual traffic content being load balanced.
References: http://dizdarevic.ba/ddamirblog/?p=187