What's now a long time ago I wrote an entry about an oddity in our network setup that was the result of historical evolution. At the time we had our printers on a physically separate set of switches, which carried a single active VLAN for a private sandbox network that all of the printers were on. These switches had shrunk from their original purpose of carrying several of our public networks that weren't on our normal core switch environments because they'd started out as a "protocol based VLAN" on our very old switches, a feature our new(er) core switches didn't support, and we thought we'd had decent reasons to not split the public networks into real separate VLANs.

Well, time marches on and we do turn over network gear and replace old switches, so you can probably guess what has happened since that entry . These days our 'printers' private sandbox network is merely another VLAN carried on our regular switch fabric, with all of its old switch infrastructure long since retired. We also bowed to the forces of convenience and put all of our public networks to our core switches as tagged VLANs, not just one of them. In the process I believe we changed the VLAN number for the primary network of our old "protocol based VLAN" setup, which probably happened as we turned over core switches. Exactly when all of this happened isn't clear to me at this late date, but it may have been starting even at the time when I wrote the original entry .

(That all of this is fuzzy to me at this point is another example of how I'm not going to accurately remember our past setups and thus we should periodically write either or both of end of service notes or periodic overviews and descriptions of our current (network) environment .)

Large scale changes in network setups can be hard to do all at once (or at least require some degree of downtime), but sometimes you can do them incrementally as you deploy and replace switches. Plus, there are hacks to do things like run old and new VLAN numbers in parallel, with one set on old infrastructure and a new set on new infrastructure, crossing over from the old to the new infrastructure through things like untagged ports (if you have only a few VLANs that are renumbering).

It's also worth remembering (even if only for myself for future use) that today's awkward, historical network and other situations aren't something you're stuck with forever. Even if you don't want to make a 'big bang' style disruptive change, you can probably fix the situation slowly over (enough) time. The process of changing over may be awkward (as our printers network was, as covered in the original entry ), but things can evolve.

(This does require that you have a long enough planning horizon to carry this all out. We're lucky enough that we can do this sort of thing ; other environments aren't as stable as ours. But our infrastructure is surprisingly stable .)