A company has set up an IPsec tunnel between its AWS environment and its on-premises data center. The tunnel is reporting as UP, but the Amazon EC2 instances are not able to ping any on-premises resources.
What should a SysOps administrator do to resolve this issue?
To resolve the issue of the Amazon EC2 instances not being able to ping on-premises resources despite the IPsec tunnel being up, the SysOps administrator should enable route propagation for the virtual private gateway in the route table that is assigned to the subnet of the EC2 instances. This allows the VPC route table to automatically learn and propagate the routes for the on-premises network, ensuring that the EC2 instances know how to reach these on-premises resources through the IPsec tunnel.
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.
According to the question, the issue is “the Amazon EC2 instances are not able to ping any on-premises resources”. Opening IMCP port for the EC2 security group won’t resolve EC2 inability to ping the on-prem resources. Enabling pinging on the on-prem resources could resolve this issue but this is not what option A is saying. Therefore, option C is a reasonable solution to this issue and it is the only option that makes sense.
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.
https://docs.aws.amazon.com/vpc/latest/userguide/WorkWithRouteTables.html#EnableDisableRouteProp
ccccccccccccccccccCCC
UP = up (in constract with 'down')
Going with C