Mailinglist Archive: opensuse-edu (132 mails)

["Mark Evans" <mpe@xxxxxxxxxxxxxxxxxxxxxxxxxxx>]

> I may be trying to teach Granny to suck eggs here but you cannot flout the
> rules.
> 
> Subnet masks must always be a series of 1's then 0's. You cannot mix and
> match. The mask is used to separate the host and network portions ie the
> last non-zero octet must always be one of 192, 224, 240, 248 or 252 (254 is
> allowed in Class A in the second or third octet or Class B in the third
> octet but not in either case the fourth octet). 128 is also not allowed to
> be the next octet from the standard netmask for each class in subnetting.
> 
> All the following netmasks allow no hosts
> Class A netmasks 255.255.255.254 or 255.128.0.0.0
> Class B netmasks 255.255.255.254 or 255.255.128.0
> Class C netmasks 255.255.255.254 or 255.255.255.128

The idea of classes A, B and C is something like a decade out of date,
the original idea was that the subnet mask could be worked out by
looking at the first octet of the IP address.


-- 
Mark Evans
St. Peter's CofE High School
Phone: +44 1392 204764 X109
Fax: +44 1392 204763