Why Does Linux Mint Not Connect to the Internet Through Ethernet Cable?

Question

For some reason my linux mint v20.1 has not been able to connect to the internet through the ethernet cable that is plugged into it. I know that the ethernet cable is not the problem because it works with other computers. This computer was also working with the ethernet cable a few days ago. The ethernet port is glowing orange, meaning that it is not an external problem because it is detecting it. This is the output of lspci (for broadcom):

02:00.0 Ethernet controller: Broadcom Inc. and subsidiaries NetLink BCM57780 Gigabit Ethernet PCIe (rev 01)

This is the output of lsmod (for tg3):

tg3      172032  0

And when I tell system log with this command to report that the card has been initialized there is no output:

dmesg | grep ether

This is also has no output:

dmesg | grep -i eno1

But this does, meaning (I think) that the cable is called eth0:

dmesg | grep eth0

The output (I have to type this out so I am going to use some imaginary variables) x = [ 1.629770] y = 0000:02:00.0

x tg3 y eth0: Tigon3 [partno(BCM57780) rev 57780001] (PCI Express) MAC address 14:fe:b5:df:5a:0c
x tg3 y eth0: RXcsums[1] LinkChgREG[0] MIirq[0] ASF[1] TSOcap[1]
x tg3 y eth0: dma_rwctrl[76180000] dma_mask[64-bit]
x tg3 y enp2s0: renamed from eth0

but actually, it has been renamed to enp2s0. So I tried this:

ifconfig enp2s0

Output:

enp2s0: flags=4098<BROADCAST,MULTICAST> mtu 1500
     ether 14:fe:b5:df:5a:0c txqueuelen 1000 (Ethernet)
     RX packets 0 bytes 0 (0.0B)
     RX error - dropped 0 overruns 0   frame 0 
     TX packets 0 bytes 0 (0.0B)
     TX errors 0 dropped 0 overruns 0   carrier 0   collisions 0 
     device interrupt 16

This is a remade version of my original post: Why Won't Linux Mint Connect With Ethernet?

I added a lot more information that will hopefully help with figuring out the issue.

Answer 1

Okay, I think you found it. This means that the card is installed and recognized:

enp2s0: flags=4098<BROADCAST,MULTICAST> mtu 1500
     ether 14:fe:b5:df:5a:0c txqueuelen 1000 (Ethernet)
     RX packets 0 bytes 0 (0.0B)
     RX error - dropped 0 overruns 0   frame 0 
     TX packets 0 bytes 0 (0.0B)
     TX errors 0 dropped 0 overruns 0   carrier 0   collisions 0 
     device interrupt 16

But notice that there is no IP address listed? This means that the ethernet card is not configured. You need to enter a configuration using either NetworkManager, netplan, or whatever system your distro is using.

To quickly check whether it's working you can configure it manually (here I assume you have a router at 192.168.1.1 and you can use the 192.168.1.137 address):

ifconfig enp2s0 192.168.1.137 netmask 255.255.255.0
route add -net default gw 192.168.1.1

Now you should be able to ping 192.168.1.1 and, if Internet is connected, something farther like one of the Google nodes at 8.8.8.8.

You may want to do a

grep -r eth0 /etc

to see whether there is a configuration extant, it's simply not working because it uses the old eth0 moniker instead of the enp2s0.