It is our amazing new 10G switch.
Purchased in early 2017 as part of the revamp of our vm cluster. In the past, it was configured with 4 10G SFP+ modules, which connected it to Murasoi, Maltair, Medico, and Molmol. It also had a 1Gbit link to curviceps to connect it to the rest of the network.
After much progress buying more 10G-SR fibre gear, Walnut currently handles SFP+ links to Murasoi, Molmol, Maltair, Medico, Loveday, Motsugo and Magikarp. It is now the "centre" of the machine room network, connecting to Kerosene via a 10G link and Curviceps via 2 1Gbit links aggregated with LACP.
There are currently plans to upgrade the last few server connections (Mudkip and the new Cisco UCS, in particular) to 10G fibre.
See Network for more information.
Ubiquiti EdgeSwitch 16-XG that features 12 SFP+ slots and four RJ45 10GBASE-T ports.
Walnut has a nice web interface at walnut.mgmt. Alternatively a terminal interface can be opened by ssh or through the console port on the switch.