Out of band management is a process for accessing and managing network devices and infrastructure at remote locations through a separate management plane from the production network. Out of band management requires network devices to be managed using a different set of IP addresses than the ones used for in-band management or data traffic. This provides a secure and dedicated alternate access method to administer connected devices and IT assets without using the corporate LAN.

An incorrect subnet mask can cause a host to be unable to communicate with other devices on the same network or on different networks.
A subnet mask defines the range of IP addresses that belong to a network segment. It also determines the network ID and the host ID of an IP address.
If a host has a subnet mask that does not match the subnet mask of the router or the file server, it will not be able to determine the correct destination for its packets.
For example, if the router and the file server have a subnet mask of 255.255.255.0, and the host has a subnet mask of 255.255.0.0, the host will think that the router and the file server are on the same network as itself, and will try to send packets directly to them without using the router as a gateway. However, the router and the file server will not recognize the host as a valid source, and will drop the packets or send back an ICMP destination unreachable message.
To fix this issue, the host needs to have the same subnet mask as the router and the file server, or use a subnet mask that is compatible with the network topology.
An incorrect DNS server, IP class, or TCP port would not prevent the host from pinging the router, as these are not relevant for ICMP echo requests and replies. They could affect other types of communication, such as name resolution, routing, or application layer protocols, but not the basic connectivity test of ping. Reference:
Subnet Masks - CompTIA Network+ N10-008 - 1.3
Troubleshooting IP Addressing - CompTIA Network+ N10-008 - 5.1