[SOLVED] Connected to network but can't reach internet

[Cupain7]

I use Debian 10 on a desktop PC with ethernet connection. This morning, my house has been connected to the fibre instead of ADSL.
Since, Debian connects to the ethernet network (1000MGB/s max), but I can't reach internet.
I tried with Windows 10 (Dual boot), it works. I tried to connect the ethernet cable on my laptop with debian 10, it works...
So the problem is on my Debian PC, but I don't know where to check !
Can someone help me ?

[Head_on_a_Stick]

Can we see the output of

Code: Select all

ip a
ip r
cat /etc/resolv.conf

[Cupain7]

Thanks for your help

ip a

Code: Select all

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: enp34s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
    link/ether 00:d8:61:4e:71:de brd ff:ff:ff:ff:ff:ff
    inet 192.168.1.25/24 brd 192.168.1.255 scope global dynamic noprefixroute enp34s0
       valid_lft 43149sec preferred_lft 43149sec
    inet6 2a01:e34:ec66:ef60:b7cc:6bab:f852:68f9/64 scope global dynamic noprefixroute 
       valid_lft 86352sec preferred_lft 86352sec
    inet6 fe80::aa4a:6ce7:ac99:2668/64 scope link noprefixroute 
       valid_lft forever preferred_lft forever
3: docker0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default 
    link/ether 02:42:37:ab:10:b3 brd ff:ff:ff:ff:ff:ff
    inet 172.17.0.1/16 brd 172.17.255.255 scope global docker0
       valid_lft forever preferred_lft forever

ip r

Code: Select all

default via 192.168.1.254 dev enp34s0 proto dhcp metric 100 
172.17.0.0/16 dev docker0 proto kernel scope link src 172.17.0.1 linkdown 
192.168.1.0/24 dev enp34s0 proto kernel scope link src 192.168.1.25 metric 100 

cat /etc/resolv.conf

Code: Select all

# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
#     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
nameserver 192.168.1.1

[Cupain7]

I tried sharing my phone connection via USB, and it's the same : Debian connects to the phone network, but can't reach internet.
So, the installation of the fibre should be a coincidence. I have something soft-locked...
Something like it already happened some years ago : it was because I didn't correctly closed a VPN connection. I checked this time, I don't have VPN enabled.

The problem could come from here : after the fibre installation, i started my computer, and Debian asked me for restarting it to perform an important update. Which sounds strange, because it didn't have internet access. Maybe an update was processing, and didn't finish correctly ?

[p.H]

Code: Select all

default via 192.168.1.254

Code: Select all

nameserver 192.168.1.1

Usually, the internet box acts as default router and DNS server, so both settings are the same address.
Maybe either setting has been fixed in the network configuration (resolvconf, NetworkManager, /etc/network/interfaces, /etc/dhcp/dhclient.conf...).

[Cupain7]

You're perfectly right, I fixed my ip adress once, when i hosted a server.
I don't remember where, but i'm checking ! Thanks

[Cupain7]

OK, I changed nameserver in resolv.conf for FrenchDataNetwork DNS instead of 192.168.1
Not sure to understand why, but it works. I don't know why I put 192.168.1 whereas I wanted to avoid my provider DNS ! Is that automatic, or i just forgot why i did that ?
Nevermind, thank you for your help !

[Head_on_a_Stick]

OK, I changed nameserver in resolv.conf for FrenchDataNetwork DNS instead of 192.168.1

You should actually read the content of that file. The comment at the top makes a useful observation. Hint: edit /etc/resolvconf.conf instead.

[p.H]

edit /etc/resolvconf.conf

Unless the DNS address was pushed to resolvconf by one of its clients (networking, NetworkManager, dhclient...)