How to set the Firefox proxy settings

If you want to use Firefox behind a proxy and need to tell it to bypass a range of addresses, this is how you do it:
Press Alt-O, Network, Settings

In 'no proxy for', use the following values.


10.0.0.0/8 will allow 10.*.*.*

10.0.0.0/16 will allow 10.0.*.*

10.0.0.0/24 will allow 10.0.0.*

In summary, the number after the '/' indicates how many bits to 'keep or mask', while allowing any value in the remaining bits of the address, starting from the left.

For example, 1.2.3.4/16 will cover the range 1.2.0.0 - 1.2.255.255
(i.e. keep the left 16 bits = 2 octets = '1.2')

For more examples of how this works, visit this CIDR calculator


ps: Comments and/or links to this article are most welcome!