Can depend to devices connected to your switches, settings related to idle state and wake-up functions of devices, IGMP Snooping possibilities of switches and gear.

Normally a connection locally on your home-network from PC to a NAS, a maximum of about 110-112 MegaBYTE per/sec could be possible, or calculated to Megabit about 900 Mbps instead of a miserable speed of 100 Mbps. Not to mention less than 10 Mbps speed.

Maybe a handsome subject translated by Google see < THIS ONE >

Thanks for your help. The low speed is only over the router (with a direct connection). I tried all the connection options. I think to reset the router to default settings….

Try other LAN-cables as well.
E.g. when one core (out of is damaged, local speed shall sink form 1 Gig to 100 Mbps.

Hi @Geekay. Welcome to our Forum here. I noticed @Babylonia has already provided you with some useful information. I'm curious whether a different LAN cable has resolved the issue. 

Hi @Geekay. Since you haven't replied in this topic anymore, I expect for the issue to have been resolved. Please let us know if you do have any other questions. 

Thank you. I shall