And for added clarity "full duplex" means it can send and receive data (packets) at the same time

Again, check the Synology status and you will see the negotiated speed there, like my screenshot. 

You have tried reterminating both ends? It's unusual (certainly not unheard of) for there to be a fault mid run.

Yes I did. Close inspection of the existing cable looks like it may have been re-purposed from another installation and has been stapled poorly. Hence the decision to replace.

peejayw:

 

Yes I did. Close inspection of the existing cable looks like it may have been re-purposed from another installation and has been stapled poorly. Hence the decision to replace.

 

stapled?  Do you mean with a stapler? 

Yep, looks like a common or garden stapler :-(

peejayw:

 

Yep, looks like a common or garden stapler :-(

 

dont use staples… Ethernet cables don’t like staples… actually no cable should ever be stapled. 

I sure won't be :-)

There are plastic-coated 'staples' with the right shape for the cable, to be applied using either a hammer or a special staplegun. They're perfectly suitable.

I don't think they're what you're talking about, though.

No, these just looked liked large paper staples.

peejayw:

 

No, these just looked liked large paper staples.

 

"My Internet is not working"

😜

It’s a NAS device…

NETWORK ATTACHED…. STAPLE.

Just an update for anyone interested. The under-floor cable is definitely faulty and I will have to replace it. However, access to one end is going to be a nightmare. The person who initially installed it must have been a contortionist :-(

On the bright side, I removed the router that I was using as an AP and instead installed a Grandstream GWN7660E and now I have wifi through the house. Those abominable wifi repeaters have gone and everything works so much better. In particular I have noticed that the connection to my wifi cameras is greatly improved with none of the previous stuttering.

     >The under-floor cable is definitely faulty and I will have to replace it. However, access to one end is going to be a nightmare. The person who initially installed it must have been a contortionist<

Do you have access to a skinny teenager?   Another trick if straight run, securely bind the new cable to end of old one and see if it will pull through.