On Mon, 29 Dec 2014 14:23:56 -0500 (EST) Jay Ashworth <jra@baylink.com> wrote:
From an intermediate routing standpoint, though, it would be easier to add an *adjacent* block, not one halfway across the address space, no?
One never knows how the address space is carved up. Changing what were once deemed reasonable addressing ideas, ultimately becoming grossly suboptimal, often loses out to competing interests. A long time ago, I arrived at a network where there were two major sites with many LANs at each site. Generally speaking each LAN was a department, but a department spanned both sites. Each department/LAN at a site started off with less than a /25 worth of nodes. This was apparently all done at a time when RIPv1 was the norm and multiple subnet sizes were not widely deployed if even available in the gear deployed. The arrangement I inherited was such that a department was assiged a /24, with the lower half (a /25) network at one site, and the upper half at the other. As long as the organization's assigned /16 always used /25's per network and departments split between sites fit into the /25 things might have been fine for awhile. By the time I arrived the address space was impossibly fragmented with some router interfaces having many secondaries as departments arose, grew, split, ceased to exist and new sites came online. This had the now predictable effect of turning a seemingly nice day one addressing plan into a fragmented and secondary mess. That was over 15 years ago and there are still remnants of the originally addressing plan in place. I wouldn't be too surprised or even too concerned about these sorts of configurations that appear poorly designed in hindsight. They are natural for most any complex system as it evolves. It is all part of the fun. John