On Thu, Feb 04, 2021 at 08:23:39PM -0500, Stefan Monnier wrote: > > I powered the router down again, plugged its WAN port into one of the > > LAN ports of the ISP-supplied router, and brought it back up. > > I you sure you plugged your ISP-router into the WAN port of your > (Buffalo) router and not into one of the LAN ports? > > The behavior you describe would be easy to explain if it was plugged > into a LAN port (or if the WAN port was somehow bridged with the LAN > ports) since in that case you'd have basically a single network with > packets forwarded between the two routers, and two DHCP servers, making > it quite possible that a DHCP request received on your router ends up > being answered by the ISP router instead (since the request is > broadcasted to all connected machines). >
So thanks to everyone who replied to this thread, some really great links and suggestions which I am following up. One thing for the record, there is absolutely no possibility I connected the LAN port to LAN port -- the LAN port on the ISP's router is plugged into the WAN port of the old router. That has been checked, double checked and triple checked. Whatever is causing it, it isn't that. There is a switch on the back of the old router, with 2 settings, "AP" and "WB". "AP" is obviously "Access Point". Not sure yet what "WB" stands for but I suspect some of the links you guys supplied will help me figure that out. The router is set to "AP" -- I _think_ it always has been, but I might be misremembering that and the switch could easily enough have been moved in the course of an international move or while lying around on my spare bedroom floor for the best part of a year. Anyway -- thanks very much all for the input supplied, I have plenty reading to do! :) Mark
