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The ethernet was working a few days ago. But now I can only use the slow wifi.

Here is the output of ifconfig (the first 2 are Ethernet interfaces):

enp0s31f6: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
        ether 1c:1b:0d:67:e9:74  txqueuelen 1000  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
        device interrupt 16  memory 0xef300000-ef320000  

enp4s1: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
        ether d4:6e:0e:00:8c:e9  txqueuelen 1000  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 1228  bytes 91800 (91.8 KB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 1228  bytes 91800 (91.8 KB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

wlx1cbfce2bb446: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 10.0.7.126  netmask 255.255.0.0  broadcast 10.0.255.255
        inet6 fe80::d273:a97:e944:dc81  prefixlen 64  scopeid 0x20<link>
        ether 1c:bf:ce:2b:b4:46  txqueuelen 1000  (Ethernet)
        RX packets 157  bytes 36587 (36.5 KB)
        RX errors 0  dropped 9  overruns 0  frame 0
        TX packets 192  bytes 27036 (27.0 KB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

I tried ifdown but it says unknown interface

$ sudo ifdown enp4s1
Unknown interface enp4s1

$ sudo ifdown enp0s31f6
Unknown interface enp0s31f6
0

How about restating the interface?

First you add

network
version: 2
renderer: networkd
ethernets:
    [your interface name]:
        dhcp4: true
        dhcp6: true

to

*.ymal file under

/etc/netplan/

and then

sudo ifdown [interface name] && sudo ifup [intreface name]

Please tell if this does not help you!

  • Please see the end of of post. I get Unknown interface error – draw May 6 at 14:53
  • I have edited my post. Please check it – MR. ROBOT May 6 at 15:09
  • 1
    An 18.04 system uses netplan or Network Manager, not /etc/network/interfaces anymore. – Thomas Ward May 6 at 15:25
  • You are right. I have edited my post. – MR. ROBOT May 6 at 15:38

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