I would recommend that instead of trying to kill the after-market for older Cisco equipment, Cisco should instead start looking at such a market as a lucrative cash-cow.

If a small company could get their hands on used Cisco equipment for cheap, but they had to pay for the software to license and use it, I dare say that many would do just that. This doesn't encourage knock-offs - the serial number of the unit should be tied to the license key; no valid serial (or duplicate in the DB) would result in a visit from the Cisco-License-Nazi (NO LICENSE FOR YOU! NEXT!). Got a legit machine? There are ways to determine this; if yours is legit, then Cisco's got the address of the idiot with the fake. Can we say "litigation"?

Maybe it's not as much income as a new machine/software package, but then again, positive cash flow is positive cash flow. And, once they've got Cisco equipment and software in the company, then they're positioned to start applying gentle but firm pressure to upgrade, upgrade, upgrade!