If you have the power of multiple servers connected to a UPS, you probably need to shut them down when the power goes down and before the UPS runs out of juice. Unless your UPS can be connected to the network, you usually can only connect a single device to it using good old serial or brand new USB. That single host now knows about the UPS status, but what about all the other systems?...
So, like me, you want to have redundancy for your virtual machine network. For my lab setup, I use a refurbished Cisco router 3825 with two gigabit interfaces, two Procurve 2810-24G and a small server with 4 gigabit interfaces for the ESXi. You just have to: team the NICs on the ESXi (use src-mac + beacon probing), use port-channel on the Cisco router and src-mac too, configure the switches exactly the same way as if there wasn’t any redundancy, add a link between the two switches and configure it to transmit the VLANs you need, don’t forget to add STP on the switches and put a high priority (low number) on the link between the switches....