[Bug 2142118] Re: Kernel 6.8.0-100: route cache corrupts external IPs as broadcast on systems with VLAN interfaces

Thanks for testing Reinier.

I spoke with the Kernel Team, and they decided they aren't going to
release 6.8.0-103-generic early, or do any emergency respins. The
current plan is to release the 2026.02.09 on its expected schedule, so
if we look at https://kernel.ubuntu.com/, it should reach -updates the
week of 9th of March.

You can keep using 6.8.0-103-generic, and I hope it remains stable.

If you find any more issues, please do file a bug and let us know.

Thanks,
Matthew

** Changed in: linux (Ubuntu)
Status: New => Fix Released

** Changed in: linux (Ubuntu Noble)
Status: New => Fix Committed

** Tags added: verification-done-noble

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https://bugs.launchpad.net/bugs/2142118

Title:
Kernel 6.8.0-100: route cache corrupts external IPs as broadcast on
systems with VLAN interfaces

Status in linux package in Ubuntu:
Fix Released
Status in linux source package in Noble:
Fix Committed

Bug description:
Description:
- Regression from: 6.8.0-94 (works) to 6.8.0-100 (broken)
- Setup: Dual default routes — physical interface (enp0s31f6, DHCP, metric 100) + VLAN (enp0s31f6.3, static, metric 200)
- Symptom: ip route get 8.8.8.8 returns broadcast 8.8.8.8 ... cache <local,brd> — kernel classifies external unicast IPs as
broadcast, blocking all outbound UDP/ICMP
- Impact: All outbound DNS, NTP, ping fail with "Permission denied"
- Workaround: sudo ip route flush cache temporarily fixes it, but it recurs
- Confirmed: Booting into 6.8.0-94 resolves the issue

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