Can I use an USB Ethernet adapter to connect Sony Ericsson Xperia Active to a wired Ethernet LAN? Due to my profession I have to connect to wired-only LAN-attached devices (like managed switches, routers set-top-boxes, etc.) frequently to access their configuration interfaces via Telnet/SSH/HTTP. I am totally tired of carrying a bag with a laptop with me wherever I go.

Now I am planning to buy an Android smartphone and feel like I'd like it to be Sony Ericsson Xperia Active which is pretty tough (I need it very much as my phones fall from my hands/table/pocket hundreds times a year), reasonably robust and stylish.

It would simplify my life significantly if I could connect it to wired Ethernet networks.

Is this possible?

I don't mind using a hack or a custom firmware like Cyanogen Mod. I've already got a USB NIC based on ASIX AX88772 chip (which is detected by Ubuntu out of the box and, AFAIK, is also compatible with XBox, PS3 and Apple Macs).
Not an answer but a good alternative. Buy this inexpensive wifi powerbank. 

This is practically a very portable wifi router. I bought and use one and so far its great. Can also be an inexpensive Mifi device using a 3G dongle, and a backup battery for your phone.