@granroth That smells like bad port quality + cheap cable. Won't create problems in TCP, but UDP suffers quietly, and ends up wrecking your nerves, by breaking DNS. Start wireshark and you will see the the tale-telling "Spurious TCP retransmission".
@granroth said in Enabling access between LAN and other non-WAN interface:
I followed @viragomann's line of thinking and focused very intently on the devices in question. Specifically, I started by concentrating multiple hosts on the single proven-working Omada managed switch and experimented with them being part of OPT5 or part of IotVLAN or both and then in each case, connecting and receiving connections from/to LAN, OPT5, and IotVLAN.
When the dust settled and I collated all of the successful and failed attempts, it was pretty obvious that the root problem was my original SG116E "Smart Switch" since it was only connections to and from that switch that potentially failed. As long as the hosts were all on the Omada switch -- regardless of what LAN or VLAN they were on -- they would work with each other. Furthermore, any hosts on the Omada switch could typically connect to any host on the LAN network, even though that went through the suspect "Smart Switch".
My plan, now, is the replace the "Smart Switch" with my new Omada switch and see if all of my problems just disappear.