Azure Interview Questions Part #5



Q #1 What are Azure disk reservations?

Q #2 Difference between Basic and Standard Public IP.

Q #3 Can we re-store the azure VM on a different region if yes how ? what are the prerequisite.

Q #4 What is TCP Idle Timeout for a Load Balancer.

Q #5 How can we change the TCP timeout ?

Q #6 What you think happen to the backend pool VM of a LB lost internet.

Q #7 What is the fix of above situation?

Q #8 What changed in the instance restore and how does it impact your costing.

Q #9 What RBAC role is needed for AD sync configuration.

Q #10 Is there any Port blocked by Azure globally if yes which one.



Q #1 What are Azure disk reservations?

Disk reservation is the option to purchase one year of disk storage in advance, reducing your total cost.
Azure disk reservation provides the option to purchase Premium SSDs in the specified SKUs from P30 (1 TiB) up to P80 (32 TiB) for a one-year term. There is no limitation on the minimum amount of disks necessary to purchase a disk reservation. Additionally, you can choose to pay with a single, upfront payment or monthly payments. There is no additional transactional cost applied for Premium SSD Managed Disks. Reservations are made in the form of disks, not capacity.


Q #2 Difference between Basic and Standard Public IP

Standard IP is the new and started with the introduction of IP SKU before that all were Basic. Standard IP provides more facility as compare to basic and allocation method is Static only unlike Basic where its both dynamic and static.
Standard IP is secure by default means you need to explicitly whitelist IP but for Basic its open for all if NSG is not applied.
Standard IP is Zone redundant and used by standard load balancers unlike Basic which cant be used in case of Zones.


Q #3 Can we re-store the azure VM on a different region if yes how ? what are the prerequisite.

 Cross Region Restore (CRR) allows you to restore Azure VMs in a secondary region, which is an Azure paired region. This option allows you to restore the VM or its disk if there's a disaster in the primary region.
To choose this feature, select Enable Cross Region Restore from the Backup Configuration blade
Pre-requisite – Vault must be created as GRS redundancy. This is in pre-view but soon be GA.

Q #4 What is TCP Idle Timeout for a Load Balancer

In its default configuration, Azure Load Balancer has an idle timeout setting of 4 minutes. If a period of inactivity is longer than the timeout value, there's no guarantee that the TCP or HTTP session is maintained between the client and your cloud service.
When the connection is closed, your client application may receive the following error message: "The underlying connection was closed: A connection that was expected to be kept alive was closed by the server."
A common practice is to use a TCP keep-alive.
TCP keep-alive works for scenarios where battery life isn't a constraint. It isn't recommended for mobile applications. Using a TCP keep-alive in a mobile application can drain the device battery faster.


Q #5 How can we change the TCP timeout ?

We can configure the TCP Timeout on instance level Pubilc IP or on Load balancer
On lB we can change it under load balancing rule and on Public IP we can change under Configuration , by default it is  4min and it could be upto 30 mins.


Q #6 What you think happen to the backend pool VM of a LB lost internet.

LB must be internal Standard LB. This is a known situation because incase of internal std LB , outbound NAT is not available until outbound connectivity defined explicitly.


Q #7 What is the fix for above situation?

You can define outbound connectivity using an outbound rule to create outbound connectivity for VMs behind an internal Standard Load Balancer with these steps:
Create a public Standard Load Balancer.
Create a backend pool and place the VMs into a backend pool of the public Load Balancer in addition to the internal Load Balancer.
Configure an outbound rule on the public Load Balancer to program outbound NAT for these VMs.


Q #8 What changed in the instance restore and how does it impact your costing.

Instance restore doesn’t restore in seconds but quite fast as compare to usual way restore its because snapshot stays in the storage account for 2 days by default and you can change it upto 5 days so time saved in rehydration or data transferring from vault to storage account. You would be charged for the extra data (snapshot) stored in storage account. To be precise earlier recovery point created when snapshot transferred to the vault but now with this feature or upgrade recovery point created as soon as snapshot is finished and can be used to restore.


Q #9 What RBAC role is needed for AD sync configuration.
Global Admin

Q #10 Is there any Port blocked by Azure globally if yes which one.

Yes there is Port 25 is blocked globally for security reasons but you can open request to MS

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