If a web server is returning strange responses after being moved to a reclaimed subnet, what should be investigated first?

Investigating DNS should be the first step when a web server is returning strange responses after being moved to a reclaimed subnet. DNS plays a critical role in translating domain names into IP addresses, allowing clients to reach the correct server. If a web server has been relocated to a new subnet, there’s a possibility that the DNS records associated with that server have not been updated to reflect its new IP address. This could lead to clients attempting to connect to the old IP address, resulting in unexpected behavior or errors.

Furthermore, if other resources, such as the web server’s dependencies or linked services, still reference the previous DNS records, they may also fail to function properly. Therefore, ensuring that the DNS records are current and pointing to the right network location is essential to diagnose and resolve the issue effectively.

While other factors, like DHCP, orphaned services, or stale network access control lists, could potentially contribute to problems, ensuring proper DNS resolution is foundational since it directly impacts how clients access the web server.