The subnet mask is most likely containing an error that prevents the application server from communicating with the newly installed database server. The subnet mask is a binary number that defines how many bits of an IP address are used for the network portion and how many bits are used for the host portion. The subnet mask determines which devices belong to the same network or subnet and can communicate directly with each other without routing or switching devices. The subnet mask of the database server is 255.255.O.O, which means that all 32 bits of its IP address are used for the network portion and none for the host portion, which is invalid and makes it unreachable by any other device on any network or subnet. The subnet mask of the application server is 255.O.O.O, which means that only 8 bits of its IP address are used for the network portion and 24 bits are used for the host portion, which is also uncommon and makes it incompatible with most networks or subnets. References: [CompTIA Server+ Certification Exam Objectives], Domain 4.0:
Networking, Objective 4.1: Given a scenario, configure network settings for servers.