Determining whether devices are on the same subnet

To determine the subnet, the local device’s IP address is compared to the remote device’s IP address (figure A-6). Each address’s octets are compared or not compared, 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’s address and the remote device’s IP address are unmasked.

Unmasked octets are compared (indicated by ? in figure A-6).

If the subnet mask octet contains the value 0, the related octets of the local device’s and remote device’s IP addresses are masked.

Masked octets are not compared (indicated by X in figure A-6).

If the unmasked octets of the two IP addresses match (indicated by = in figure A-6)(example 1), the two addresses are on the same subnet.

If the two unmasked fields do not match (indicated by ≠ in figure A-6) (example 2 and example 3), the addresses are not on the same subnet.

 

 

Example 1

Example 2

Example 3

Local IP Address:

192.168.254.254

 

192.168.254.254

 

192.168.254.254

 

Subnet Mask:

255.255.0.0 (?.?.X.X)

255.255.0.0 (?.?.X.X)

255.255.0.0 (?.?.X.X)

Remote IP Address:

192.168.2.25

 

190.190.2.25

 

192.190.2.25

 

 

 

 

 

 

 

 

 

Match?:

=.=.X.X Match

..X.X No match

=..X.X No match

 

 

(Same subnet)

(Different subnet)

(Different subnet)

Figure A-6 Comparing the IP addresses

MTPX Plus Twisted Pair Matrix Switchers • Ethernet Connection

A-7

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Extron electronic MTPX Plus Series manual Determining whether devices are on the same subnet