Its a Surf SOHO router with 6.3.3 build 1068 f/w. I created two VLANS in the Network>Network Settings dialog with inter-VLAN routing disabled and two individual APs. One is intended for wireless IoT devices and the other for wireless guests, the purpose being to isolate either from our WiFi client PCs on the trunk/untagged LAN. The issues (no wired VLAN DHCP and no WAN,) arose when I tried to assign a wired port to the first VLAN and applied to both after I created the second. It persists even if that VLAN is wired only.
The Ethernet WAN port is connected to a LAN port on an AT&T provided Pace/Arris 5031NV residential Gateway, not one of the more infamous ones, but one with ports on its own LAN that shouldn’t be open. The RG’s WiFi is disabled. When the WAN comes up, it provides the SOHO with one of its private IPs in 192.168.1.xxx, although when the new SOHO is fully working, it will be placed in DMZ+ and receive the public IP with the expectation that the SOHO can protect itself from probes and exploits from outside and any potentially corrupted IoT client. It appears it will work that way, but only wirelessly and if only if any wired device is on trunk/any.
When and while any single access port is configured, the WAN fails DNS test or ping, whichever is configured as its health check method and there is no connectivity between the WAN and any of the SOHO’s three APs, the LAN or either VLAN. The defined access port delivers no DHCP and thus no connection; if I unplug from the access port and plug to any of the remaining trunk/any ports, the SOHO delivers an IP in the 192.168.50.xxx range but no WAN connectivity, until and unless the access port is returned to the trunk/any default.
My next step, probably not tomorrow because of other time commitments, will be to try TCPDUMP:DHCP to examine what, if anything, is happening to DHCP requests on that access port, not that I will necessarily be able to do anything about that, nor will it necessarily diagnose the WAN issue.
I’m forever a networking newbie, having troubleshot DHCP problems before, but that was long ago. Thanks for your help.