wifi ok; ethernet ok but firefox says "Unable to connect"

[Huib]

Hello, please can someone give me some help.
My OS: Linux Mint 21.3 Cinnamon (version 6.0.4) kernel 5.15.0-151-generic; intel I5-4460 @3.2 GHz x4; mem 7.7 GiB; graphics Advanced Micro Devices Tahiti pro [Radeon HD 7950/8950] OEM display server X11.

What's the problem: as soon as I establish a wifi connection everything is fine, but I prefer my ethernet connection.
That connection doesn't work. Firefox reports: "Unable to connect" as soon as I switch off the wifi connection.
Looking to the network connections I see:
Wired: connected 100 Mb/s. IPv4Address 192.168.178.26; IPv6 Address 2001:1.........; DNS4 192.168.178.1 (indeed my routers address)
Wifi: ZiggoXXXXXX signal strength good; link speed 780 Mb/s; etc. etc.; Default route 192.168.178.1 DNS 62.179.104.196 213.46.228.196
As firefox is working good via the wifi connection I presume the firewall is not causing the problem.

Next to that Linux machine there is a W10 machine (that I want to replace by my Linux one) that doesn't have wifi and works smoothly with my ethernet cables.
I approach this forum via this W10 machine.
So router and provider are ok: the W10 machine on ethernet cable is fine.
Thanks to everybody who would be so kind to lend a helping hand! Huib Huijnen

 

[f33dm3bits]

Can you open a terminal and share the output of the following?

ping -c3 192.168.178.1
ping -c3 8.8.8.8
ping c3 google.com
nmcli connection con show

 

[Brickwizard]

as soon as I establish a wifi connection everything is fine, but I prefer my ethernet connection.
That connection doesn't work. Firefox reports: "Unable to connect"

you should not have both connecting at the same time, try disabling the wi-fi and enabling Ethernet in the network settings

 

[Condobloke]

Let us know if you have any success with the above suggestions.

I have another suggestion but will wait for your reply re above

 

[Condobloke]

You had a similar problem a while ago

H

Thread '"some, not all sites state "Unable to connect", wile others just work fine'

Mar 13, 2025

L.S.
Fresh installed Linux Mint 21.1 Cinnamon. Some sites show up flawless (for instance https://keepassxc.org/download/#linux;
https://freefilesync.org/download.php and https://wikipedia.org) but most approaches render "Unable to Connect". examples are "startpage.com", "https://www.linuxmint.com" and many more.
There is a wired connection AND a wireless connection. Switching off the wireless one didn't change a thing.
Who can give me a clue what's wrong here?

Some patience will be helpful! Please, a step by step approach as Linux still is quite confusing!
Thank...

• Huib
• most sites persistent "unable to connect" some flawless
• Replies: 15
• Forum: Linux Networking

Post #6 from @CaffeineAddict solved your problem there