The EC2 instances in your VPC are unable to resolve on-premises resources. What are two possible reasons for this problem? (Choose two.)

September 14, 2021 by Admin

You have a hybrid environment in which your VPC queries your on-premises DNS server for up resources in your environment. The EC2 instances in your VPC are unable to resolve on-premises resources.

What are two possible reasons for this problem? (Choose two.)

  • Your NACL is blocking UDP port 53 outbound 
  • Your security group is blocking port 53 inbound
  • Your NACL is blocking TCP port 53 outbound. 
  • Your on-premises firewall is blocking port 443

Explanation:
DNS requires TCP and UDP port 53.

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