When Cisco made its 802.11n 1250-series AP announcement a few months ago, one of the more interesting aspects was its claim that the PoE capabilities in some existing desktop switches and blades for its chassis-based solutions would be able to power all the radio chains in its dual-radio 802.11n access points and that it would only need a software upgrade to access them. Cisco was intentionally vague in its communications and presentations. It wanted to present to the public the greatest degree of backward compatibility and support even while it was verifying the hardware capabilities and coding the software.
In the original press briefing there were references to 3750-series desktop switches, but it appears that only the PoE-enabled models of Cisco's new 3750-E, with modular power supplies, will power the new dual-radio 802.11n APs, not the older 3750 or 3750G ones. Even though the 3750-E was announced earlier this year, there is a significant installed base of legacy 3750s that will not be able to power Cisco's dual-radio 802.11n APs.
Similiar requirements apply to the Catalyst 4500/6500 line cards. Only the latest blades will support Cisco's dual-radio 802.11n APs, and customers will likely need to verify the capacity of their switch's power supply/supplies.
The software that supports the increased PoE levels will be available around the end of the year.
For shops that have the newest switches and blades, this software upgrade works out well, but for those using legacy gear, does it make sense to rev their Ethernet ports when the industry is just a year or so away from ratifying the IEEE 802.3at standard? Cisco will argue that future revisions of their access points will draw even less power, so if you upgrade now you'll be able to power any Cisco access point. On the other hand, at some point there will be 802.3at peripherals that need powering and should that necessitate another round of upgrades?
If you're planning to upgrade your switches anyway, the extra power comes for free, but if you're not, you might just consider using mid-span power injectors in the interim and wait until 802.3at switches hit the market.