Subnet Masks And Octets; Determining Whether Devices Are On The Same Subnet - Extron electronics DXP 44 4K PLUS User Manual

Subnet masks and octets

The subnet mask (see figure 52) is used to determine whether the local and remote devices
are on the same subnet or different subnets. The subnet mask consists of four numeric
octets separated by dots. Each octet can be numbered from 000 through 255. Leading
zeros, up to three digits total per octet, are optional. Each octet typically contains either 255
or 0. The octets determine whether or not the same octets of two IP addresses should be
compared when determining if two devices are on the same subnet.
255 indicates that this octet is
compared between two IP addresses.
Typical Subnet Mask: 255.255.0.0
Figure 52. Subnet Mask and Octets

Determining whether devices are on the same subnet

To determine the subnet, the local device IP address is compared to the remote device IP
address (see figure 53). The octets of each address are compared or not, depending on the
value in the related subnet mask octet.
• If a subnet mask octet contains the value 255, the related octets of the local device
address and the remote device IP address are unmasked.
Unmasked octets are compared (indicated by
• If the subnet mask octet contains the value 0, the related octets of the local device and
remote device IP addresses are masked.
Masked octets are not compared (indicated by
If the unmasked octets of the two IP addresses match (indicated by
figure 53), the two addresses are on the same subnet.
If the two unmasked fields do not match (indicated by an unequal sign in figure 53,
examples 2 and 3), the addresses are not on the same subnet.
Example 1
Local IP Address: 192.168.254.254
Subnet Mask: 255.255.0.0 (?.?.X.X)
Remote IP Address: 192.168.2.25
Match?: = . = .X.X — Match
(Same subnet)
Figure 53. Comparing the IP Addresses
0 indicates that this octet is not
compared between two IP addresses.
Octets
?
Example 2
192.168.254.254
255.255.0.0 (?.?.X.X)
190.190.2.25
≠ . ≠ .X.X — No match
(Different subnet)
DXP HD 4K PLUS Series • Reference Information
in figure 53).
in figure 53).
n
in example 1 of
=
Example 3
192.168.254.254
255.255.0.0 (?.?.X.X)
192.190.2.25
= . ≠ .X.X — No match
(Different subnet)
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