Kernel 6.8.0-100 network problems

[daver1730]

I’m using Kubuntu 24.04 LTS with kernel 6.8.0-100 but others have the same problem with Ubuntu.

When the 6.8.0-100 kernel was installed a few days ago, my Internet connection became very intermittent. Firefox became almost unusable with each web page often needing several retries to make it load.

A web-search on that kernel showed this page on Reddit with others reporting the same problem, and as the others there say, rebooting into the older kernel 6.8.0-94 removes the problem (scroll down to the last few comments):

https://redd.it/1qzd9fz

Looking at the logs in /var/log doesn’t show anything obvious, so I don’t really know where the dysfunction is located, other than the fact that it only manifests with the latest kernel.

Suggestions for debugging this, please?

(As a temporary workaround, I’ve manually edited grub.cfg to boot the older kernel by default for now.)

[surajprajapati002]

Identify Your Network Hardware + Driver

Boot into 6.8.0-100 (the bad kernel) and run:

lspci -nnk | grep -A3 -E 'Ethernet|Network'

If you’re on Wi-Fi also:

iw dev

This tells us:

• Exact chipset
• Which kernel module (driver) is in use

Very likely candidates:

• Realtek (r8169, r8125)
• Intel (iwlwifi, e1000e, igc)
• MediaTek
• Broadcom

Kernel updates often regress specific drivers.

Check for Driver Errors (Not in /var/log)

Modern Ubuntu doesn’t log much in traditional /var/log. Instead use:

journalctl -k -b

Then filter for networking:

journalctl -k -b | grep -iE 'eth|enp|wlan|wifi|firmware|r8169|iwlwifi|igc'

Also check for:

• firmware load failures
• link flapping
• resets
• timeouts

If you see things like:

NETDEV WATCHDOG
link down
firmware crashed
tx timeout

Check for Packet Loss (Kernel 100)

While running the bad kernel:

ping -i 0.2 8.8.8.8

If you see intermittent packet loss or latency spikes, that confirms low-level network issues (not DNS or Firefox).

Also try:

mtr 8.8.8.8

Very Common 6.8 Regression: Realtek r8169

If your NIC uses r8169, this kernel series introduced changes that broke stability for some chips.

Check:

lsmod | grep r8169

If yes, try this test:

sudo ethtool -K enpXsY tso off gso off gro off

(replace enpXsY with your interface)

If that improves stability → it’s a driver offload regression.

Permanent test workaround:

Create:

sudo nano /etc/modprobe.d/r8169.conf

Add:

options r8169 disable_msi=1

Then:

sudo update-initramfs -u

Reboot.

If Intel (iwlwifi or igc)

Check firmware version:

dmesg | grep iwlwifi

Sometimes installing newer firmware helps:

sudo apt install --reinstall linux-firmware

Better Workaround Than Editing grub.cfg

Do not edit grub.cfg manually — it gets regenerated.

Instead:

sudo nano /etc/default/grub

Change:

GRUB_DEFAULT=0

to:

GRUB_DEFAULT="Advanced options for Ubuntu>Ubuntu, with Linux 6.8.0-94-generic"

Then:

sudo update-grub

That safely pins the older kernel.

Or simpler:

sudo apt-mark hold linux-image-6.8.0-100-generic

If You Want Proper Debugging

Compare working vs broken kernel logs:

Boot 94:

journalctl -k -b > kernel94.txt

Boot 100:

journalctl -k -b > kernel100.txt

Then diff:

diff kernel94.txt kernel100.txt

Look for network-driver differences.

[juergh]

Kernel regressions should be reported on Launchpad:

https://bugs.launchpad.net/ubuntu/+source/linux/+filebug

Or run the following in a terminal (running the broken kernel):

$ sudo ubuntu-bug linux

[daver1730]

Many thanks for that comprehensive debugging guide.

I had Intel 82574L network hardware and the e1000e kernel driver.

The problem has completely vanished for the moment.

I can only think that the suggested reinstallation of the linux-firmware package must have changed something, even though the same version of that package had already been installed.

[rubi1200]

Staff note to users:

While we certainly appreciate all efforts to help, content that appears to be AI-generated needs to be acknowledged.

@system

If you know how to make good use of AI and are sure that your result is valid, you may use it in helping you to formulate your answer, but please acknowledge that you have used it. Any posts which turn out to be entirely or largely AI, especially without acknowledgement, will be removed and infractions may result.

@surajprajapati002 Welcome to Ubuntu Discourse and thanks for trying to help

Please review the Support and Help posting guide I linked to.

Thanks