IPv4 CIDR Block

Discussion in 'Cloud Computing' started by _51040, Jan 7, 2019.

  1. _51040

    _51040 New Member

    Dec 6, 2018
    Likes Received:
    Hi Team,

    I am trying to create a VPC and 2 subnets within it Private and Public. The IPv4 CIDR block address of my VPC is and for private subnet is also the same. when I am trying to use a IP address within a range of the VPC CIDR address I get an error "Must be a valid IPv4 CIDR". so can somebody explain me how is the IPv4 CIDR address range defined within a VPC? I also need to understand how exactly does this IP address allocation works.

  2. Yogitha Koppal

    Yogitha Koppal Active Member
    Simplilearn Support

    Dec 28, 2018
    Likes Received:
    When you create a VPC, we recommend that you specify a CIDR block (of /16 or smaller) from the private IPv4 address ranges. If you need more information regarding this kindly refer to IPv4 address ranges as specified in RFC 1918.

    You can create a VPC with a publicly routable CIDR block that falls outside of the private IPv4 address ranges specified in RFC 1918; however, we refer to private IP addresses as the IPv4 addresses that are within the CIDR range of your VPC.

    For further information and reference kindly go through the link below ( AWS documentation)

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