RE: Stupid Question maybe?

["Naslund, Steve" <SNaslund () medline com>]

> Why do you think the network portion needs to be contiguous?

Just because some equipment at one time let you configure a non-contiguous mask does not make it correct configuration. 
 Please come up with any valid use case for a non-contiguous network (note NETWORK, not any other purpose) mask.

> Well, it does now. But that was not always the case.

It has ALWAYS been the only correct way to configure equipment and is a requirement under CIDR.  Here were your 
commonly used netmasks before CIDR/VLSM :

255.0.0.0
255.255.0.0
255.255.255.0

Which one is not contiguous?

> https://www.quora.com/Why-is-the-subnet-mask-255-255-255-64-invalid/answer/Patrick-W-Gilmore

In this example, the writer used it as a parlor trick to actually break a network.  That's why you don't do it and it 
was never a good configuration.  It just exploited a UI that did not validate the netmask.

> https://www.quora.com/Why-is-the-subnet-mask-255-255-255-64-invalid

In the second cited link, they are talking about using a non-contiguous mask in an access control function.  That is 
perfectly valid to do, it just is not a NETmask anymore.  By definition a netmask identifies the network portion of an 
address.  In the cited example they are defining a group of subnets to an ACL.

Steven Naslund
Chicago IL

> --
> TTFN,
> patrick