@rob4999 Unfortunately, you will need to add a managed switch, to get the new subnet to normal devices. See here: https://community.tp-link.com/en/business/forum/topic/590922

@PCHIT Check you ACL settings, make sure you have IP Group LAN deny to 192.168.178.0/24, and direction is LAN-WAN.

@antonioabb Policy routing, choose All LAN use low ping WAN as priority.

@ChiefyChief IoT devices won't use so much bandwidth, so it's not a problem for router. ER605 can handle 100 normal devices, ER7206 can handle more; However if all of these IoT devices require...

@papac0rn What's the IP address of your Codium Networks router? Try set up a static IP on ER7206 WAN/LAN1. If the problem is related to DHCP, a static IP can solve it.

@Ondulado It could be an issue caused by old firmware. I took a screenshot of firmeare release notes: In short, today's web browser won't support CPE firmware older than 20190620. You have two...