While reviewing the backup logs a server administrator notices that a backup job for an application server on the same subnet has failed. Which of the following is MOST likely the problem?

Backup solutions often rely on a remote agent or service running on the target application server to facilitate communication with the backup server, collect data, and manage the backup process. If this agent is not running, the backup server cannot connect to or initiate a backup of the application server, leading to a job failure.

A failed management card would affect remote out-of-band management of the server, but typically would not directly cause a backup job failure initiated by software on the server itself.

A proxy server is typically used for internet access or specific internal routing, and is unlikely to block direct communication between a backup server and an application server on the same subnet.

While a hardware firewall could block access, it's less likely than an agent failure for servers on the same subnet, which implies internal network communication without significant perimeter defenses between them, making an agent issue more probable.