Ubuntu 16.04 LTS网络故障求助：有线检测无网、WiFi选项缺失、USB热点连而不通

Hey there, let's work through these network problems you're facing on your HP-ac039TU running Ubuntu 16.04 LTS. I've run into similar hardware-specific quirks before, so here's a step-by-step breakdown for each issue:

1. Wired connection detected but no internet access #

• Check basic connectivity & IP config
  • First, run ip addr in the terminal to check your wired interface (usually named enp*). If you see an IP starting with 169.254.x.x, that means your system couldn't grab a valid IP via DHCP.
  • Try pinging a public IP directly: ping 8.8.8.8. If this works, the problem is with DNS settings:
    • Edit your DNS config with sudo nano /etc/resolv.conf and add these lines:

      nameserver 8.8.8.8
      nameserver 8.8.4.4
      

      Save with Ctrl+O and exit with Ctrl+X.
  • If the ping fails, check your default route with ip route. If no default route is listed, add one manually (replace [GATEWAY_IP] and [WIRED_INTERFACE] with your actual values):

    sudo ip route add default via [GATEWAY_IP] dev [WIRED_INTERFACE]
    

• Reset Network Manager
  • Restart the service to refresh connections:

    sudo service network-manager restart
    

  • If that doesn't help, reset Network Manager's state:

    sudo rm /var/lib/NetworkManager/NetworkManager.state && sudo service network-manager restart
    

2. WiFi toggle option missing entirely #

HP-ac039TU typically uses a Realtek RTL8723BE wireless card, which has known compatibility quirks with Ubuntu 16.04. Try these steps:

• Verify hardware & driver status
  • Run lspci | grep Network to confirm your wireless card model. If it's RTL8723BE or similar:
    • Install the required firmware first:

      sudo apt update && sudo apt install linux-firmware
      

    • If firmware alone doesn't work, install the DKMS driver package for Realtek cards:

      sudo apt install rtlwifi-new-dkms
      

• Check physical/software toggles
  • Make sure your laptop's physical WiFi switch (if present) is turned on, or press the Fn+Fxx key combo (usually F12 on HP laptops) to enable WiFi.
  • Force-enable WiFi via terminal:

    nmcli radio wifi on
    

• Check BIOS settings
  • Reboot your laptop and enter BIOS setup (usually by pressing F10 at boot). Ensure the "Wireless LAN" option is set to Enabled.

3. USB hotspot shows connected but no internet #

Since this worked before on Ubuntu and works on Windows, it's likely a config glitch:

• Validate USB interface connectivity
  • Run ip addr to check the USB network interface (usually usb0 or enp0s*). Confirm it has a valid IP (not 169.254.x.x).
  • Ping 8.8.8.8 again—if this fails, your system isn't routing traffic through the USB hotspot.
• Reset USB & network services
  • Disconnect the USB hotspot, then restart the USB service:

    sudo service udev restart
    

  • Reconnect your phone's hotspot and check again.
• Adjust Network Manager settings
  • Open Network Manager, find your USB hotspot connection, go to IPv4 Settings.
  • Set the method to Automatic (DHCP) if it isn't already. If that fails, try manual settings:
    • IP address: 192.168.42.100 (or any unused IP in your phone's hotspot subnet)
    • Netmask: 255.255.255.0
    • Gateway: 192.168.42.1 (most Android hotspots use this)
    • DNS servers: 8.8.8.8, 8.8.4.4
• Rule out firewall interference
  • Temporarily disable the firewall to test:

    sudo ufw disable
    

  • If internet works now, re-enable the firewall and add a rule to allow hotspot traffic:

    sudo ufw enable && sudo ufw allow in on [USB_INTERFACE]
    

If none of these steps resolve your issues, share the output of dmesg | grep -i network or journalctl -u NetworkManager—that will help pinpoint the exact problem.

内容的提问来源于stack exchange，提问作者Arijit Gupta