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Problem

From these screenshots below, I believe that I have successfully configured my Ethernet adapter.

Using lshw to showcase the established interfaces

Using ifconfig to show the configuration of the network interfaces

After configuring my Ethernet adapter, I connected local device to my desktop and attempted to ping it to test whether there is a successful connection. Below is the result of that ping:

Result of pinging 4 packets to device IP address

Initially, there was some weirdness surrounding whether the interface was able to detect a connection.

Showing that I set my Ethernet IPv4 settings to manual instead of automatic DHCP

When this was set to Automatic (DHCP), the Wired part of the settings would fail to connect with Ethernet. As a result, I manually configured my address, netmask, and gateway, as you can see through the previous screenshot. After this, the settings menu began to show that I was connected to some device via Ethernet, as shown here:

Showing that the UI says that the Ethernet is connected

Therefore, my problem is that I should be able to ping the device that is directly connected, but I am unable to. I hooked up the device to another desktop via Ethernet and saw successful pings, so I wanted to know why the pings were failing for a device directly connected to the desktop in question.

What I've Tried

  • I have done power cycling on both the device and my desktop, and I have checked for loose connections

  • I have looked into the potential of ACLs, rate limiters, and other such firewalls, blocking the receipt of packets. I am very new to network security, so I might have missed something, but I do not believe that this is the issue, since nothing really showed up.

  • I have tried directly adding the IP I'm trying to ping and its host name into my route

  • On that note, I have run traceroute -I 192.168.137.11 and only the IP of my PC appeared

Possibly Useful Background

The desktop in question was newly built with a motherboard with a component that only works for kernel versions 5.15 onwards. The desktop is running Ubuntu 20.04 because I need to use a feature that is exclusive to the MoveIt version for ROS Noetic, among other things. Thus, I am currently using kernel version 5.15.31. My Ethernet interface is a Realtek RTL8125. Installing the drivers for it was a hassle because most everything I've tried through the Realtek website:

https://www.realtek.com/en/component/zoo/category/network-interface-controllers-10-100-1000m-gigabit-ethernet-pci-express-software

and through using sudo apt-get install r8168-dkms have failed, mostly due to issues involving Linux headers. After removing several other kernel versions, removing and reinstalling other packages, what eventually allowed me to interact with the Ethernet interface (I think) was by running:

sudo apt install realtek-r8125-dkms

I believe the successful installation of this package, as well as the earlier screenshots, indicates that the driver has been installed, but I don't really know if this is true, and I have no idea if the kernel version that I am using is interfering at all with the networking.

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  • Welcome to AskUbuntu, I heard one of the network devices is old and they are confused with 10-T, 100-TX and 1000-T(x). Or simply the router rejects 'ping'. for my 2 cents. Apr 24, 2022 at 7:08

1 Answer 1

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I suppose that your Ethernet device name is enp7s0.

Please, try some tests:

Test 1: Physical and link layer check

Disable Wi-Fi interface. Connect peer device to the Ethernet port and wait when the link LEDs next to connectors are on. Then use ethtool command.

First line is needed only if the ethtool is not installed:

sudo apt-get install ethtool
sudo ethtool enp7s0

Search for these lines (speed, duplex, negotiation type and link) in command output:

    Speed: 1000Mb/s
    Duplex: Full
    Auto-negotiation: on
...
    Link detected: yes

All values should look as in my example. All these parameters are independent of the OSI layer 3 setting. It does not matter if IP parameters are set to dynamic/manual/no IP address etc.

Problem values (any of listed): speed = 10 Mb/s, duplex = half, link detected: no

Test 2: ARP records and network neighbors

Leave the peer device connected. Set the IP address of Ubuntu from the same IP network as peer device (e.g. 192.198.1.0/24), but different last byte. Switch Ubuntu Ethernet interface off and on. Then get the network neighbors and their MAC addresses in Ubuntu.

ip neigh
arp -an

You should see at least one line containing a MAC address of peer device. Both commands generates similar output.

Test 3: Network data capturing and listing

Use tcpdump or tshark or wireshark to capture network frames/packets and watch if there is ARP or DHCP communication and if any responses from other devices are received.

sudo tcpdump -i enp7s0 arp or udp port 67 or udp port 68

Eventually check if any communication is captured at all.

sudo tcpdump -i enp7s0

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