Second PC disconnects the first PC. Why?

[Lekro44]

Hello,

I have a very simple home network. 2 desktop PCs. Windows 10 Pro, latest drivers (including NIC, downloaded from ASUS for the specific motherboard models), simple modem-router combo from ISP (Sagemcom FAST@3686).

Every setting is at it's default value when it comes to networking, only the DNS is changed to Cloudflare's 1.1.1.1.

What happens is when the first PC is being used and later we power on the second PC, the connection for the first PC is dropped. Small yellow ! mark on the icon, PC still has the same IP, no internet, can't ping the other PC or anything on the network, can't access router config page.

ipconfig /release then /renew doesn't work.

It can only be resolved by either rebooting the first PC or disabling and reenabling the NIC and after that it still gets the same IP as before.

The two PCs have different IPs.

This issue occures randomly and never in the other direction (like first PC disconnects the second PC).

I tried assigning IP reservations, giving the DHCP lease more time before renewal, etc.

Help me please.

 

[kanewolf]

Have you tried a factory reset on the Sagemcom -- https://www.router-reset.com/reset-manuals/Sagemcom/FST-3686 ?

 

[Lekro44]

Thanks for the answer, yes I have tried.

 

[kanewolf]

Are the PCs wired or wirelessly connected?

 

[Lekro44]

Both on wired, directly to the sagem. Every other device on the network (phones) have different IP assigned by DHCP so no IP conflict is present.

 

[Lekro44]

Can anyone give me a list of possibilities I can check in case I missed something during troubleshooting?