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/P...
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