Help troubleshoot network issues

[SAguy]

So I know my way around networking for the most part, but I've got a family member who is having internet issues. Hard to get detail since some of the family is in hospital (covid) and those at home are not technically inclined, but here's what I know.

• They have fibre and the fibre is up
• They have a main router which provides wifi and has some LAN devices connected
• Then they just recently plugged in another wifi repeater via LAN in the granny flat
• In the granny flat they are able to connect to the wifi repeater wifi and use the internet (so fibre is fine)
• In the main house, I think they can connect to the wifi and internet, but LAN devices can't connect to internet
• If they unplug the LAN cable from their tv, and connect via wifi it works fine, plug LAN back in and internet is dead on tv
• They think the LAN internet stopped working when they plugged in the granny flat's wifi repeater
• I don't know if they're using one SSID or different for the repeater vs main house

I don't know yet what the brands of devices are, nor whether the above has been communicated correctly.
What I'm thinking is that they just plugged in the repeater and there's perhaps IP address conflict, or conflicting DHCP servers. There's also a possiblility of LAN ports being broken on the router, but I kind of ruled that out now since the repeater is connected via LAN and working fine.

I'm going to remote onto a working laptop on their side later and have a look around, hopefully they have usernames/passwords available for the routers.

Any other ideas on what it could be and what I could check?

 

[My_King]

Yeah not too much to go on.

Check if the device get IPs and what range of IPs.

Maybe they are getting the right range but DNS is screwed up on a 2nd DHCP server

 

[SAguy]

Turned out it was the second extender that was plugged in.

It had it's own SSID and (here's the strange part) when you connect to it's SSID you sometimes get a DHCP address from the primary router or you get a DHCP address from itself.

For now I just had them unplug it, and all back to normal.

 

[HavocXphere]

Yeah repeaters are Satan’s spawn. Endless stability issues...

 

[Gerry]

1. disable dhcp server on the wifi repeater
2. make sure wifi is disabled on the tv when it's connected via network cable

 

[Jbn222]

1. disable dhcp server on the wifi repeater
2. make sure wifi is disabled on the tv when it's connected via network cable

I am using two old D-Link routers as repeaters connected to ethernet cables.
Do I need to have different DHCIP IP ADDRESS RANGES (10.0.03 to 10.0.0.254) for each router?
The Router IP ADDRESS is 10.0.0.2



Please advise