Initially, I told myself I wasn’t going to spend an entire blog post to the new 3850 switch. Presented on Cisco Live London, it was just a new series of Catalyst switches with all existing functionality plus some new things like the integrated WLC. Not really interested in anything else, I got bored and Googled around to see if my WS-C3560-8PC fanless desktop switch had a gigabit equivalent. Turns out it does, with quite a few models. All fanless, PoE capabilities and some layer 3 models. But then I noticed something: some of these models had both PoE powering and PoE powered ports. So how does that work? Well, these switches have two PoE powered ports. Some power is used for the switch itself and the remainder is used in the PoE budget towards the switches. The switches can give standard 802.3af PoE at 15.4W per port, but can receive 802.3af (15.4W), 802.3at PoE+ (25,5W) or UPoE. UPoE isn’t an official standard yet, but Cisco is pushing for it and their new 3850 series supports it. It allows up to 60 Watts per port.

And then it hit me. 3850’s, compact switches, and other PoE devices like Access Points and IP Phones allow for a lot of interesting designs.


For example, using the 3850 in a stack as a core switch in an office, it’s possible to give power to fanless (silent) compact switches near the desks. The C2960CPD-8PT (what a name!) has two powered PoE uplinks so a 2 Gbps port-channel towards the 3850 stack is possible. That gives redundancy when spread over two switches, and the stack can also use StackPower. It’s max power budget is 30W, which is enough for two PoE devices, or more when using 802.3af classes or CDP PoE negotiation, e.g. many IP Phones only use 7 Watt, allowing for four on one switch. Result: it’s possible to power an entire office network directly from the core: less wall sockets needed, less cable runs. And finally, the integrated WLC on the 3850 allows all AP tunnels to terminate in the office itself, instead of going back towards a remote controller in a HQ/Data Center. This allows faster and easier access to local resources (printers, on-site servers).

The combination 3850/Compact switches allows for long cable runs without any need for a power supply anywhere in between. In the most extreme case you can bridge 500 meters with it: 3850, 100m copper  UPoE, 2960CPD, 100m PoE, 2960C, and a 100m cable run towards a mirrored setup.

So yes, when thinking about it, these new switches with new technology do allow more flexibility when deploying a network!