Isolating part of a network

[Enquiries]

I am building an RFID reader based timing system for running races. This will be a portable system for outside.I have 2 Motorola fx7400 readers connected to a TP Link wireless router via LAN. I have set the preferred client IP addresses for each reader at 192.168.0.102 and 192.168.0.103. I did this as the readers seem to need to maintain their auto DHCP selection or they become impossible to connect to when DHCP is turned off. The problem lies in when I connect the router to the internet (both wirelessly as a range extender, (preferable as this will be how I will connect to my phone hotspot in the field)) or hardwired as a secondary router, I lose communication with my readers. I suspect the internet connection is reassigning my IP addresses but I am unsure. My question is this: How can I maintain my dedicated network of readers while gaining internet access for just my laptop? I am guessing a managed ethernet switch, or is it as simple as reassigning IP addresses? Thanks for any help!

[ed]

To maintain a dedicated network for your RFID readers while allowing your laptop to connect to the internet, you can isolate the readers from the internet-facing network while still enabling your laptop to access both. Here’s how you can achieve this:

1. Use a Separate Subnet for the RFID Readers
Configure your TP-Link router to use a subnet for the RFID readers that does not conflict with the main internet network.
Example:
RFID reader network: 192.168.1.x (Router LAN IP: 192.168.1.1).
Internet-facing network: 192.168.0.x.
Ensure the router’s DHCP server assigns IPs only within the reader’s subnet (e.g., 192.168.1.100-192.168.1.200) while reserving the reader IPs as static leases.
2. Keep RFID Readers on a Separate VLAN (Preferred with Managed Switch)
If your TP-Link router supports VLANs or if you use a managed switch, you can:
Assign the RFID readers to a dedicated VLAN (e.g., VLAN 10).
Isolate this VLAN so it doesn't have internet access but allows internal communication between the readers and your laptop.
Connect your laptop to the internet via another VLAN or directly to the router's main Wi-Fi network.
3. Set Static IP Reservations in DHCP
If you don’t have a managed switch or VLAN support:
Use your TP-Link router to reserve IP addresses for your readers.
Access the DHCP settings on the router and bind the MAC addresses of the RFID readers to their respective IPs (e.g., 192.168.0.102 and 192.168.0.103).
4. Use Internet Connection Sharing or a Secondary Router
Connect your laptop to the internet (e.g., via a hotspot) and enable Internet Sharing:
Share your laptop’s internet connection with the TP-Link router.
This keeps the RFID readers on their own subnet while the laptop has access to both networks.
5. Manual Routing Configuration
Advanced option: Configure static routes on your TP-Link router:
Add a route that allows your laptop to access both the reader subnet and the internet while isolating the readers.
Troubleshooting Connection Loss
If you lose communication with the RFID readers when connecting the TP-Link router to the internet, it’s likely due to IP address conflicts or DHCP lease changes:

Ensure your laptop, hotspot, and TP-Link router are on different subnets to avoid conflicts.
Confirm the RFID reader IPs are static and not being reassigned by another DHCP server (e.g., on the main internet router or hotspot).
Recommended Setup
Use a dedicated VLAN or a separate subnet for the RFID readers.
Use your laptop as the gateway for internet access via hotspot or share the connection through the TP-Link router.