Subnet Issue

Discussion in 'Cloud Computing' started by _41100, Oct 20, 2018.

  1. _41100

    _41100 Member

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    Hi,

    My question is why my IP address in the subnet not correct as per attached image. Furthermore, I wish to understand that my VPC CIDR range I have selected as 10.0.0.0/16 which equates out to be somewhere like 65,536 Ip address. First question to this is if my VPC has 65,536 Ip address, does that mean in one single region I can have 65,536 VPC setup ? Do we really require as many as 65,536 VPC to be setup for a region

    Regarding public Subnet.

    While creating a public subnet I am using IP as 10.0.0.254/24. The first set of 3 octet I am not changing as leaving as 10.0.0 and the last octet I have given numeric value as 254 which is still less than 255, so why is it giving me invalid IP address. ?

    I am looking for a very simplified answer, as i am not from IT background, have little understanding to network.

    Looking to hear from Sonal or community.

    Thanks
    Aditya Khanna
     

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    #1
  2. Akansha Chaurasia

    Akansha Chaurasia Well-Known Member
    Simplilearn Support

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    Hi Aditya,

    In order to have a static IP address, we need to align an Elastic IP. As IP address changes once service is not in the running mode.
    We can have 65,536 VPC it totally depends on the requirement of the organization.
    When the CIDR provided 10.0.0.254/24. This value is syntactically the same as 10.0.0.0/24. They are the same because the /24 indicated that the last 8 digits (it is a 32 digit space - so 32 - 8 == 24) should be dropped and the first address used.

    Hope it helps!
    Thank you
     
    #2
  3. _41100

    _41100 Member

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    Hi Akansha,

    I am not sure if you are a moderator or one of the instructor out here, nevertheless let me put my doubt again.
    Say for example I wish to create a VPC within a region (Ohio - taking as an example) and want to give it a CIDR range as 10.0.0.0/16 = 65536 Ip addresses or host (computer) or say I am giving VPC CIDR range as 10.0.0.0/20 --> 32 -20=12, 2^12=4096. So, out here what I wanted to know here is --- can I create 65,536 or 4096 VPC connections in a region (Ohio) or this 65536 IP address allocated to my subnet ?

    so as per given example if I create a public subnet or private subnet within my VPC, the IP address allocated to both of my subnet, webserver, database server (which reside in a subnet) will be taken from 65536.

    Furthermore, I know elastic ip's are static and dont change there address once given, so dont understand your rationale of it out here in your answer that you gave. Also, I was told that we can have only 5 VPC in a any region, so it contradicts to above statement which I gave earlier. let me know which stands true. ?

    Last but not the least, 10.0.0.254/24. The value syntatically states that you can not modify first 3 octet and change the last. 32 -24 == 8 bit of last octet. In AWS 5 IP address are reserved with AWS. In any IP addressing I can have till 255 hosts, so when I took 254 which falls within 255, where does it stands wrong. I know .255 is reserved Ip's.

    I am attaching herewith a diagram which i made for vpc. please have a look and let me know if my graphical representation is all fine or not.

    Looking to hear from you or sonal.


    Thanks
    Aditya Khanna
     

    Attached Files:

    #3
  4. Akansha Chaurasia

    Akansha Chaurasia Well-Known Member
    Simplilearn Support

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    Hi Aditya,

    When you create a VPC, we recommend that you specify a CIDR block of /16 or above (smaller number = bigger space) from the private IPv4 address ranges.
    For example, if you create a VPC with CIDR block 10.0.0.0/20, it supports 4096 IP addresses. You can break this CIDR block into two subnets, each supporting 1028 IP addresses.

    the CIDR block should be chosen in consideration with the number of IP addresses needed

    5 vpc is the default limit

    Thank you
     
    #4

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