User guide

X7968 Basic Settings

6.2. How to calculate the Gateway IP after “public” IP and

mask provided by Telefonica.

Each number in the IP (or mask) separated by “.” Should be written as an 8 digit

binary number. The boolean operation “AND” must be done between IP

address and mask in a one to one basis and the the rightmost number

incremented in 1. Finally each number is again written in decimal code.

(IP AND MASK) OR 1

Operation table (truth table):

OR 0 1

0 0 1

1 1 1

AND 0 1

0 0 0

1 0 1

Example:

IP: 80.20.10.50

Netmask: 255.255.255.0

Each value is written as an 8 digit binary number and AND’ed between .

IP: 01010000 . 00010100 . 00001010 . 00110010

Mask: 1

1111111 . 11111111 . 11111111 . 00000000 AND.

01010000 . 00010100 . 00001010 . 00000000

1 OR.

01010000 . 00010100 . 00001010 . 00000001

decimal

Gateway IP: 80.20.10.1