VPC CIDR Calculations Flashcards Preview

A Cloud Guru - AWS SysOps Administrator Associate (2019) > VPC CIDR Calculations > Flashcards

Flashcards in VPC CIDR Calculations Deck (18)
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1
Q

What is the largest CIDR block range in AWS?

A

10.0.0.0/16

2
Q

For the certified SysOps certification. which CIDR value will you be tested on?

A

IP address Count

3
Q

There are four values that a CIDR block range provides, what are they?

A

Netmask
First IP
Last IP
IP address Count

4
Q

How many IP addresses are included in 10.0.0.0/16

A

65,536

5
Q

In AWS, what is the smallest number you can put after the forward slash in a CIDR block? ex. 10.0.0.0/x

A

16

6
Q

In AWS, what is the largest number you can put after the forward slash in a VPC CIDR block? ex. 10.0.0.0/x

A
  1. This will provide 16 IP addresses
7
Q

After every iteration of one after the forward slash, available IP addresses are removed by how many?

A

Available IP addresses are reduced by one half.

/26 = 64 IP addresses. /27 = 32, /28 = 16, and so on.

8
Q

In calcuating how many IP addresses your VPC needs, remember that AWS reserves a number of IP addresses that you will not have access to. How many IP addresses does AWS reserve?

A

5

9
Q

The AWS SysOps test will be primarily concerned aout your ability to clacluate which CIDR block ranges?

A

/24 through /28

10
Q

How many IP addresses in /24

A

256 - 5 reserved

11
Q

How many IP addresses in /25

A

128 - 5 reserved

12
Q

How many IP addresses in /26

A

64 - 5 reserved

13
Q

How many IP addresses in /27

A

32 - 5 reserved

14
Q

How many IP addresses in /28

A

16 - 5 reserved

15
Q

You need a small VPC with only a few IP addresses and decide that a /29 will be sufficient. You get an error when you attempt to create it. What’s the likely problem?

A

AWS does not allow VPCs created with a CIDR range smaller than /28

16
Q

You need to create a VPC with 50 IP addresses available, what is the most appropriate CIDR block range?

A

/26. This provides 64 IP addresses, minus 5 reserved, which equals 59 IP addresses.

17
Q

You need to create a VPC with 200 IP addresses available. Which CIDR range is most appropriate?

A

/24. This provides 256 IP addresses, minus 5 reserved, which equals 251 IP addresses available.

18
Q

The SysOps exam asks you to calculate a CIDR block range that will provide 60 available IP addresses. You answer /26 since it provides 64 IP addresses. You later find out your answer was wrong. Why might this be?

A

You forgot to consider the reserved IP addresses. Since you need 60 available IP addresses, a /26 will only make 59 IP addresses available after the 5 reserved IP addresses. Therefor the approriate answer would be /25.