Yesterday the Comcast guys said they would put in a new line from the sidewalk box to my house and that it would likely happen in a week or two. They also said I didn’t have to be home, but I would be called in advance so I know when they will be coming. Last night I went to bed at 4:10 am after my last Interact post. This morning I am awakened by the door bell at 7:45. (Doesn’t matter that he didn’t call as cell phone was off and I close office door so as not to hear answering machine.) It’s my new cable run! And he asks me to help him because the cable the cable is extremely tight due to it making at least one 90° turn inside my outside wall. So he attaches the new cable very securely to the old one and as he pulls the old end from the sidwalk box end, I push and jiggle the new one from the wall end. I have of course done this hundreds or thousands of times with my installers, but never before in black long Johns and a down parka. It was 30 degrees out this morning.
gateway only has the 10.0.0.1 IP on the LAN side. On the WAN side it's a different one - so you CANNOT connect to his gateway coming from outside with that IP address. The connection would reach YOUR gateway first; if it also has the 10.0.0.1 IP, then it would answer the request. If by some reason it has a different IP address it might try to route the request to 10.0.0.1 to the WAN - but your neighbors' gateway would still not respond to that request because it does not have 10.0.0.1 on the WAN side.
The only way you can reach his gateway is if your PC has a route via the LAN/WIFI to it. So.. perhaps your PC also had a Wifi connection to your home LAN? And via that other supposed WIFI connection to the neighbor, it would reach his gateway. There's no other way, sorry.
My intuition also says it must be WiFi, but I haven't been able to figure out the route. So thank you very much for engaging in this sleuthing with me. My desktop PC has no WiFi, only Ethernet.
But do you also have access points, extenders or wifi repeaters? All it takes is a misconfigured/unconfigured one on each side.
Yes. I have an eero mesh network: one eero 6 Pro set in Router mode is wired to the Bridged XB7 gateway in my office. A second eero Pro (not the new 6 model, but they are compatible) is at the far end of the living room. Configuration is automatic via the eero iOS app. Only the first one attached to the gateway is in Router mode. The second (and any additional ones added to a network) is automatically configured as an AP. The 2nd eero connects to the first by WiFi. If it were connected to a living room switch, would that create a loop because of 2-way communication between the eeros on the office and living room switches? eero recommends that only the first/router eero be connected by Ethernet.
I had a Netgear 1200 EoP pair set up between the office and the living room, but that became unreliable so I replaced it with a 50 ft. CAT6. This model doesn't have WiFi, but only a LAN port on each one. More recently I hooked them up again to send a signal to my original living room 8-port D-Link gigabit switch because I needed more than the 4 ports the EtherREGEN provides. This would have the 2 living room switches connected by 2 parallel lines coming from the living room switch, one on CAT6 and the other being the AC powerline. As there is no wired or wireless cross connection between the EtherREGEN and D-Link switches in the living room, I don't think there is a loop there.
I'm not familiar with this product, but... does your neighbor also have one? If they share the same network credentials, that could be the missing link.
He doesn't have a Comcast security router.
AndrewFG also mentions above that ISPs frequently add a public WIFI to their routers/gateways. True, but this WIFI network MUST be isolated from the regular home network, so it should not allow any bridging. If it does, then Comcast is reaaaaaaly terrible as this would be a huge security/privacy violation. If this were the case, the proverbial fecal matter would have hit the rotating propeller blades a long time ago.
On my phone I see an XFINITY (secured network with the words "Connect to Xfinity WiFi here." and I also see xfinitywifi (unsecured) with "Connect to Xfinity WiFi here." I cannot connect to either of them. They don't ask for a password, but just ask me to move closer. Their MAC addresses don't match any of the 3 on the bottom of my Comcast gateway. They only have medium strength so I suspect they are from neighbor houses, rather than my gateway (there are no businesses near me). I just looked in my Xfinity Hotspot app and the only one showing withn a few blocks is the one in my iPhone. By zooming in on their map I could see my phone moving from one end of my house to the other - ain't GPS grand? So those Xfinity networks may be associated with neighbors' Comcast gateways, but not as public hotspots. The app asked me to join the Xfinity hotspot network and I of course declined. Before putting the gateway in Bridge mode, I named its WiFi TUNEFINITY and of course that is no longer showing up in my network list. I think this joined-with-neighbor network problem is over for now. Since I put my gateway in Bridge mode, there have been no new appearances of their devices on my network and the old ones have moved down the Recently Online list and disappeared. So I think the transgression was happening on the Comcast TUNEFINITY network and not on the eero network.
The loop usually requires a cable with both ends connected to the same switch; or 2 cables connecting 2 switches together (without port-aggregation enabled); or 3 cables connecting the switches/repeaters/access points in a loop A<->B<->C<->A; or N cables and N devices forming a loop. If any of those links is not a cable but is instead a Wireless extender/repeater, it's still a link, so that can also form a loop. Even a device with 2 ports (like a NAS), should only have 1 cable connected unless your Switch is properly configured for port-trunking/LACP on the 2 ports. And definitely don't connect each port to different switches when the switches are also connected together.
I only have one cable connecting NAS to switch. So I think I'm loop free unless you tell me otherwise. I will hold off calling my IT guy if MC25 keeps working and my network stops crashing. But if things get weird, I will get him over here.
PS: Comcast does have this multifamily package to connect houses together in some way, though I think it's just a contract bundling multiple house connections. Technically it's likely still the same, FTTH/FTTB/FTTx.
That link gives an error message, even with trying some variations on it.