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. Reference: [CompTIA Server+ Certification Exam Objectives], Domain 4.0:

Networking, Objective 4.1: Given a scenario, configure network settings for servers.