Exam AWS Certified SysOps Administrator - Associate topic 1 question 348 discussion

UP = up (in constract with 'down')

Going with C

If the IPsec tunnel is UP but the EC2 instances are not able to ping on-premises resources, it might be due to the security group settings. Security groups act as virtual firewalls for your instances, and you need to ensure that the inbound rules allow the necessary traffic. In this case, creating a new inbound rule on the EC2 instances' security groups to allow ICMP traffic (ping) from the on-premises CIDR (Customer-Premises Equipment, CPE) would likely resolve the issue, assuming the security groups are currently configured to block such traffic. Option A addresses the issue at the security group level by allowing ICMP traffic from the on-premises CIDR.

https://docs.aws.amazon.com/vpc/latest/userguide/WorkWithRouteTables.html#EnableDisableRouteProp

ccccccccccccccccccCCC

C: Enabling route propagation for the virtual private gateway in the route table associated with the subnet of the EC2 instances will allow the VPC route table to learn and propagate the routes for the on-premises network. This ensures that the EC2 instances know how to reach the on-premises resources through the IPsec tunnel.