Quoting out of original sequence: On Thursday, February 12, 2026 07:20:23 PM Dan Purgert wrote:
> Check the firewalls on all machines. If you forgot to change the rules > to accept the new 192.168.12.xx IP addresses, they won't let traffic > flow. Ahh, that seems a very likely possibiliity. (I say it that way because I never explicitly set up firewalls on any of the machines on the LAN, but it is quite possible that they were set up automatically when I installed the various Debians (over time), and maybe defaulted to allow traffic to / from 192.168.1.x So now I have to dig into and learn something about presumably 3 different firewalls those on Wheezy, Jessie, and Trixie -- probably take me a while and won't be a high priority project. (I got done what I needed to get done in the last few days via sneakernet, and have no desperate need at the moment.) > It's a router. Ok, but I want to clarify something: It actually has 3 (or 4) network interfaces. Network 0 -> The Internet via 5G > Network A -> 192.168.12.0 (presumably /24) (Rj45 jack) > Network B -> 192.168.12.0 (presumably /24) (Rj45 jack) And yes, all addresses are "masked" with 255.255.255.0 (i.e., /24) Ok, maybe 4: it does have WiFi capability (which, for my LAN, iirc, I managed to turn off -- at least I intended to, I'd have to double check.) I know that it does NAT between Network 0 and Network A or Network B, but I didn't think it managed to exchange anything between A and B, and I guess that thought came when searching for some explanation of why the computers can't talk to each other. But I guess my problem is more likely to be the firewalls. I'm not going to say that the TMO device is, or can be an AP (and my belief is that an AP can be accessed via WiFi or by wired connections), but, for my education, if it were an AP, would that mean that the two Rj45 Ethernet segments (and the WiFi devices (not present on my LAN) could or could not all talk to each other? > "Routing" only happens between networks (e.g. 192.168.12.0/24 to the > internet), it does not happen between two hosts on the same network. > > In fact, if your topology is > > (internet) <--> Router <--> 16-Port Switch <--> 6 other hosts > > Any traffic between any two hosts on your LAN will never cross the > "Router <--> Switch" cable. > > Could even remover the router entirely, and the hosts could still talk > amongst themselves (if you configured static IPs). Ahh, ok, thanks, that's helpful! (I might have sort of known that at one time, but the fact that I couldn't ping between machines made me doubt myself :-(
