HP Jetdirect 250M User Manual page 109

As illustrated in Example: Subnet Mask 255.255.0.0 Applied to
Class A Network, the Class A IP network address "15" has been
assigned to company ABC. To allow additional networks at
company ABC's site, the subnet mask of 255.255.0.0 is used.
This subnet mask specifies that the second byte of the IP
address will be used to identify up to 254 subnets. Using this
designation, each device is uniquely identified on its own
subnet, but company ABC can incorporate up to 254
subnetworks without violating their assigned address space.
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