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DNS in VPC

Links: 101 AWS SAA Index

DNS Resolution

  • Decides if DNS resolution from Route53 resolver server is supported for VPC.

  • enableDnsSupport: True (default)

    • It queries the Amazon Provider DNS server at 169.254.169.253 or
    • The reserved IP address at the base of the VPC IPv4 network range plus two (.2)

  • If we want to visit google.com then since we have enabled DNS support the instances can reach out to the Route53 resolver at one of the two IPs mentioned above to get the IP address of google.

    • attachments/Pasted image 20220430083904.jpg

  • If DNS Support disabled it is still possible to get DNS resolution but we will have to create our own custom DNS server.

    • attachments/Pasted image 20220430084008.jpg

DNS Hostnames

  • It is responsible for giving public DNS hostnames to the EC2 instances in that subnet. If it is false we only get a private DNS.

  • enableDnsHostnames

    • true → default VPC
      • In a default VPC instances will be assigned a public and private DNS hostname
    • false → newly created/non default VPCs
      • In a non-default VPC instances will be assigned a private but not a public DNS hostname
    • attachments/Pasted image 20220430084254.jpg

  • For it to work enableDnsSupport should be True.

  • If we use custom DNS domain names in a Private Hosted Zone in Route53 then both attributes should be true.
So for public hostnames the DNS resolution and DNS hostname of the VPC configuration should be enabled.

Last updated: 2023-03-08