@KRO-Blues 

Access Control is a routing function that allows you to control what devices are allowed on your network and which are not. This is based on the MAC address of the client device.  Your network setup is also a big part of it.  For instance you have a netgear cable router.  Is this device operating as a modem and a router or just a router?  Your C9 is it setup as an AP or is it being used as a router? 

Thanks Carl.

"For instance you have a netgear cable router.  Is this device operating as a modem and a router or just a router?"

The Netgear device is acting in both capacities Carl. As the LAN ports are full, I run a cable to the C9 to gain additional ports.

"Your C9 is it setup as an AP or is it being used as a router?"

AP being an 'access point'? No, I use it as a router Carl.

Thank you again.

@KRO-Blues 

Ok great thanks for the updated info.  Since both routers are being used as routers this usually indicates a double NAT scenario.  However this should have no affect on the access control in the TP-link router.  Try going to Advanced - Network - DHCP Server and then looking at the DHCP Client List.  See if you see your devices here first.  If you do then you can go to Advanced - Security - Access Control.  Frist check your "online" devices and see if the list matches?  If so then choose if you want this to be a whitelist (devices to have access) or a blacklist (Devices banned).  at the bottom click on the "+" to add, choose from the list or manually enter and save.  

If no devices are showing "Online" it could be due to the double NAT, and here is why.  The router may see the WAN IP address and a private IP, and therefore possible thinking the devices are not online because of this.  Really the only way to rule it out would be to put the Netgear device in brindge mode and see if the issue still occurs.  

Altrernativly if you are just trying to get more ethernet ports I would suggest an unmannaged switch as your best option.  You can pick up a TL-SG1008 for really cheap and you don't have to worry about trying to configure a 2nd device.  

Best 

Hi Carl, and thanks for your informative response!

Since both routers are being used as routers this usually indicates a double NAT scenario.  However this should have no affect on the access control in the TP-link router.  Try going to Advanced - Network - DHCP Server and then looking at the DHCP Client List.  See if you see your devices here first. 

Yes, my device was listed.

If you do then you can go to Advanced - Security - Access Control.  Frist check your "online" devices and see if the list matches?  If so then choose if you want this to be a whitelist (devices to have access) or a blacklist (Devices banned).  at the bottom click on the "+" to add, choose from the list or manually enter and save.

 Sigh, no sign of my device!

If no devices are showing "Online" it could be due to the double NAT, and here is why.  The router may see the WAN IP address and a private IP, and therefore possible thinking the devices are not online because of this.  Really the only way to rule it out would be to put the Netgear device in brindge mode and see if the issue still occurs.  

Got it. Good advice. However, I did go ahead and disable NAT boost in the C9 interface to see if devices would show up in access control, but still no go. Consequently I re-enabled NAT boost. 

Altrernativly if you are just trying to get more ethernet ports I would suggest an unmannaged switch as your best option.  You can pick up a TL-SG1008 for really cheap and you don't have to worry about trying to configure a 2nd device. 

That's a great idea, but as the C9 provides wifi to my teeange kids methinks I'll just stay with the set-up I have.

You've helped me understand the process a whole lot better, so if I want to make changes in the future I'll know how to implement them.

I thank you for your great help Carl!.