XB8-T ethernet switch compatibility

I recently switched to the Xfinity XB8-T gateway. As soon as it was up and running, I ran into problems. I had an older Netgear ProSAFE Gigabit Switch connected to the gateway's 2.5G WAN port, and I figured that was the problem. I bypassed the Netgear switch, and my speeds improved. Now, I need a list of compatible Ethernet switches (preferably unmanaged) for the 2.5G WAN port. Either my searches were worded incorrectly, or Xfinity does not have a published list. Does anyone know what unmanaged Ethernet switches play well with the 2.5G WAN port?