Neighbours Router somehow being used as my DHCP

[martdempsey]

Hi, wondering if someone resolved this.  I have the exact same problem.  Somehow my neighbors network is injected into mine, and assigns IP addresses to my devices from his DHCP.  I thought I might have an issue with one of my Access Points, so I disconnected them all, and the issue remained.  We don't use power line adapters and I'm not connected to his WIFI, this is literally from the wired lan.  The only way to stop it was to disconnect the ISP cable feeding the router.  I kept my router powered on and all my devices were re-IP'd to my network.  It's as if his network is back feeding into mine.  I edited all my devices and reserved IP address to avoid having them reconnect to his.  however, this is a short fix, need to solve the root cause.

For clarity, I use the ISP router as my DHCP server, have assigned a 10.30.x.x ip range.  this router is connected to a 16 port switch.  I connected a wireless router bridged as an AP, and have several other switches around the house and a few more bridged AP's.

I'm thinking we need to call our respective ISP to have a tech take a look, but there is cost and concerned that they won't be able to figure this one out.

[AC199]

I did resolve mine, neighbour did have a pair of power line adapters which I scanned for using the TP link software to scan a network for power line adapters. It also showed that I was connected not only to next door, but also to another neighbour over the road.

https://www.tp-link.com/uk/support/faq/259/

not sure how you can be connected if you don’t have power line adapters yourself, but that was how I fixed mine.

[martdempsey · Accepted solution]

yeah, that was the mystery. I ended up calling my ISP (SHAW) and of course they were just as baffled. I did a factory reset of my Shaw router and that seems to have fixed the issue. I did notice that prior to the reset, the MoCA was active and now following the reset its inactive by default . Anyways, seems like this fixed the problem, but I don't quite understand the causal factor.

[Keith_Beddoe]

@martdempsey 

This is a BT Retail  (UK) customer forum. 

Your ISP (Shaw),  have their own user forum.

https://support.shaw.ca/t5/discussions/ct-p/community

[ivageru]

how is this even possible?

[gg30340]

I suspect it could similar to how it may happen with power line adaptors if his neighbour was using them. 

With powerline adaptors I suspect that it is caused when the adjoining houses have a common wall and the electrical cables run beside each house's cables and the powerline adaptors may not have had their encryption turned on. 

The broadband signal radiates from one electrical circuit to the other and it acts as an aerial and is picked up by the other houses devices.

It may be the case that the Ethernet cables picked up the neighbours signal even although the Ethernet cables are meant to be shielded but I guess we will never know for sure.