This document outlines the procedure to interpret the regex used for IP range in EPL syntax.
{1,3} represents 3 digit number
[0-9] represents range number starting from 0 to 9
[0-9]{1,3} represents 3 digit number where each digit starts from 0 to 9.
Example: 000,001,002,....,997,998,999
Let me start below regex. I have highlighted the last 2 octets in red color and the first two octets highlighted in black color.
(10\.[0-9]{1,3}|172\.(3[01]|2[0-9]|1[6-9])|192\.168)\.[0-9]{1,3}\.[0-9]{1,3}
The simple [0-9]{1,3}\.[0-9]{1,3} means 000.000 to 999.999
10\.[0-9]{1,3} means 10.000 to 10.999
172\.(3[01]|2[0-9]|1[6-9]) means 172.16 to 172.19 then 172.20-172.29 then 172.30 to 172.31
192\.168 represents same 192.168
The complete meaning of this regex covers Private IP range.
10.0.0.0-10.255.255.255
172.16.0.0-172.31.255.255
192.168.0.0-192.168.255.255
Hope this document helps.
Reference: /^[0-9]{1,3}$/ - Regular Expression - Interpret Please | The ASP.NET Forums
Regular expression - Wikipedia
