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About 2 weeks ago I installed an antivirus (ESET nod32) on my Mint 20.1 server. However, after discovering that it is not at all optimized for Linux (blocked basically all my ports + connections and provided no firewall manager), I uninstalled it and my connections began working again. Recently, after toying around with setting up a Squid proxy server, my ethernet connection has stopped working again. Some diagnostics have shown that the server is detecting the connection, my driver is working just fine, and other devices connected to that router are having no issues; so I suspect it's a configuration issue. It's also worth noting that at the moment I am able to get a temporary connection with a USB wifi adapter.

Here's my output of inxi -Fxz:

System:
  Kernel: 5.4.0-66-generic x86_64 bits: 64 compiler: gcc v: 9.3.0 
  Desktop: Cinnamon 4.8.6 Distro: Linux Mint 20.1 Ulyssa 
  base: Ubuntu 20.04 focal 
Machine:
  Type: Server System: Dell product: PowerEdge T320 v: N/A serial: <filter> 
  Mobo: Dell model: 0W7H8C v: A03 serial: <filter> BIOS: Dell v: 1.5.1 
  date: 03/08/2013 
Battery:
  Device-1: hidpp_battery_1 model: Logitech Wireless Mouse Dell WM514 
  charge: 55% (should be ignored) status: Discharging 
CPU:
  Topology: Quad Core model: Intel Xeon E5-2407 0 bits: 64 type: MCP 
  arch: Sandy Bridge rev: 7 L2 cache: 10.0 MiB 
  flags: avx lm nx pae sse sse2 sse3 sse4_1 sse4_2 ssse3 vmx bogomips: 17600 
  Speed: 1200 MHz min/max: 1200/2200 MHz Core speeds (MHz): 1: 1200 2: 1200 
  3: 1200 4: 1200 
Graphics:
  Device-1: Matrox Systems G200eR2 vendor: Dell driver: mgag200 v: kernel 
  bus ID: 06:00.0 
  Display: x11 server: X.Org 1.20.9 driver: modesetting unloaded: fbdev,vesa 
  resolution: 1600x900~60Hz 
  OpenGL: renderer: llvmpipe (LLVM 11.0.0 256 bits) v: 4.5 Mesa 20.2.6 
  direct render: Yes 
Audio:
  Message: No Device data found. 
Network:
  Device-1: Broadcom and subsidiaries NetXtreme BCM5720 2-port Gigabit 
  Ethernet PCIe 
  vendor: Dell driver: tg3 v: 3.137 port: ecc0 bus ID: 01:00.0 
  IF: eno1 state: up speed: 100 Mbps duplex: full mac: <filter> 
  Device-2: Broadcom and subsidiaries NetXtreme BCM5720 2-port Gigabit 
  Ethernet PCIe 
  vendor: Dell driver: tg3 v: 3.137 port: ecc0 bus ID: 01:00.1 
  IF: eno2 state: down mac: <filter> 
  Device-3: NetGear type: USB driver: mt76x2u bus ID: 1-1.2:6 
  IF: wlx3894edc5d6e1 state: up mac: <filter> 
Drives:
  Local Storage: total: 1.46 TiB used: 12.68 GiB (0.9%) 
  ID-1: /dev/sda vendor: Dell PowerEdge RAID Card model: PERC H710 
  size: 278.88 GiB 
  ID-2: /dev/sdb vendor: Dell PowerEdge RAID Card model: PERC H710 
  size: 278.88 GiB 
  ID-3: /dev/sdc vendor: Dell PowerEdge RAID Card model: PERC H710 
  size: 931.00 GiB 
  ID-4: /dev/sdd type: USB vendor: Dell model: Internal Dual SD 
  size: 1.90 GiB 
RAID:
  Hardware-1: Broadcom / LSI MegaRAID SAS 2208 [Thunderbolt] 
  driver: megaraid_sas v: 07.713.01.00-rc1 bus ID: 08:00.0 
Partition:
  ID-1: / size: 273.00 GiB used: 12.68 GiB (4.6%) fs: ext4 dev: /dev/sda5 
Sensors:
  System Temperatures: cpu: 31.0 C mobo: N/A 
  Fan Speeds (RPM): N/A 
Info:
  Processes: 229 Uptime: 1h 24m Memory: 15.59 GiB used: 1.46 GiB (9.4%) 
  Init: systemd runlevel: 5 Compilers: gcc: 9.3.0 Shell: bash v: 5.0.17 
  inxi: 3.0.38

As well as the output for ethtool eno1:

Settings for eno1:
    Supported ports: [ TP ]
    Supported link modes:   10baseT/Half 10baseT/Full 
                            100baseT/Half 100baseT/Full 
                            1000baseT/Half 1000baseT/Full 
    Supported pause frame use: No
    Supports auto-negotiation: Yes
    Supported FEC modes: Not reported
    Advertised link modes:  10baseT/Half 10baseT/Full 
                            100baseT/Half 100baseT/Full 
                            1000baseT/Half 1000baseT/Full 
    Advertised pause frame use: Symmetric
    Advertised auto-negotiation: Yes
    Advertised FEC modes: Not reported
    Link partner advertised link modes:  10baseT/Half 10baseT/Full 
                                         100baseT/Half 100baseT/Full 
    Link partner advertised pause frame use: Symmetric
    Link partner advertised auto-negotiation: Yes
    Link partner advertised FEC modes: Not reported
    Speed: 100Mb/s
    Duplex: Full
    Port: Twisted Pair
    PHYAD: 1
    Transceiver: internal
    Auto-negotiation: on
    MDI-X: on
    Supports Wake-on: g
    Wake-on: d
    Current message level: 0x000000ff (255)
                   drv probe link timer ifdown ifup rx_err tx_err
    Link detected: yes

Any ideas?

2
  • 1
    Look at the logs! sudo journalctl -b 0 -u NetworkManager.
    – waltinator
    Mar 7 at 21:21
  • 1
    ethtool confirms that eno1 exists and has a physical connection. Your problem is at a higher level in the networking stack. Check IP addresses with ip a and the routing table with ip r first. If Linux Mint uses NetworkManager, @waltinator's suggestion is useful, but also check connections with nmcli c, and if there is an active connection, get its details with nmcli c show CONNECTION-NAME. Also look at the configuration in /etc/NetworkManager/system-connections. Mar 8 at 0:38
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After examining the output of of sudo journalctl -b 0 -u NetworkManager as suggested by @waltinator, resulting in:

<info> [...] device (eno1): carrier: link connected
<warn> [...] dhcp4 (eno1): request timed out

I finally realized that it may be helpful to check the wifi extender that my server is connected to via ethernet (gross, I know, but it works for the layout of my computers). After a quick WPS reset everything was back in working order again.

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