HP 2520-8 Configuration Manual page 77

Figure 3-7 shows the bits in the fourth block of the mask that determine the
valid subnets in which authorized stations with an IPv6 device ID of
244:17FF:FEB6:D37D reside.
FFF8 in the fourth block of the mask means that bits 3 - 15 of the block are fixed
and, in an authorized IPv6 address, must correspond to the "on" and "off"
settings shown for the binary equivalent 0000 in the fourth block of the IPv6
address. Conversely, bits 0 - 2 are variable and, in an authorized IPv6 address,
may be either "on" (1) or "off" (0).
As a result, assuming that the seventh and eighth bytes (fourth hexadecimal
block) of an IPv6 address are used as the subnet ID, only the following binary
expressions and hexadecimal subnet IDs are supported in this authorized IPv6
manager configuration:
Authorized Subnet ID in Fourth
Hexadecimal Block of IPv6 Address
0000
0001
0002
0003
0004
0005
0006
0007
Figure 3-8. Binary Equivalents of Authorized Subnet IDs (in Hexadecimal)
IPv6 Management Security Features
Authorized IP Managers for IPv6
Binary Equivalent
0000 0000
0000 0001
0000 0010
0000 0011
0000 0100
0000 0101
0000 0110
0000 0111
3-9