Your company has an on-premise environment with Active Directory for authentication and a DNS Server. You are trying to make the EC2 Instances in your AWS VPC resolve the on-premise resources , but it does not seem to work. What could be the reason for this. Choose 2 answers from the options given below

Answer options:

A.The NACL is blocking UDP port 53 outbound
B.The NACL is blocking TCP port 53 outbound
C.The Security Group is blocking port 80 Inbound.
D.The Security Group is blocking port 80 Outbound.

Answer - A and B
The Network ports used by a DNS Server is port 53. Hence these ports need to be open in the Network Access Control Lists.
During DNS resolution, DNS messages are sent from DNS clients to DNS servers or between DNS servers. Messages are sent over UDP and DNS servers bind to UDP port 53. When the message length exceeds the default message size for a User Datagram Protocol (UDP) datagram (512 octets), the first response to the message is sent with as much data as the UDP datagram will allow, and then the DNS server sets a flag indicating a truncated response. The message sender can then choose to reissue the request to the DNS server using TCP (over TCP port 53)
For more information on NACL’s, please refer to below URL:
http://docs.aws.amazon.com/AmazonVPC/latest/UserGuide/VPC_ACLs.html