#DHCP, #DNS, #IPv6, #TLS: Ihr seid anstrengend.

#pihole ignoriert nach Update standardmäßig die eigene dnsmasq-Konfiguration. Alle Hosts bekommen zwei IPv6-Gateways: Router und Pi-hole. Ziemlich zufällig wirkend hängen dann Verbindungen.

#Docker Compose-Setup mit #Coolify: Anfragen wechseln zwischen den Umgebungen, weil es kein Docker-Netz pro Umgebung gibt und per DNS-Round-Robin Anfragen zufällig an Apps verteilt werden.

#Traefik aktualisiert Zertifikate auf Basis von 2160 Stunden Gültigkeit (änderbar mit acme.certificatesDuration). #step-ca gibt Zertifikate aus, die 24 Stunden gültig sind (änderbar über authority.claims.{max,default}TLSCertDuration). Kein Wunder, dass das ganze Setup einen Tag später nicht mehr läuft.

Usw. usf.

How can I reset my DHCP configuration in a VM without creating a new virtual machine? #dhcp

https://askubuntu.com/q/1566860/612

Mood : https://www.youtube.com/shorts/o56qL2t4swA

Doing network booting (#DHCP, #TFTP, #iPXE, #UEFI, #SecureBoot)
I haven't reached the “Oh, that's why” so far. But very annoyed

https://ipxe.org/secboot
“The Secure Boot shim (e.g. ipxe-shim.efi or snponly-shim.efi) will automatically load the iPXE binary with the corresponding name (e.g. ipxe.efi or snponly.efi).”
Definitely not what's happening…
So It kept loading the wrong iPXE firmware (not the snmponly) and I kept wondering why my keyboard wasn't working :<

Fortigate is not able to get an IP address from the local DHCP on PnetLab #networking #server #2204 #vmware #dhcp

https://askubuntu.com/q/1566733/612

When two Hetzner servers died at the same time

On May 12, 2026, two of my Arch Linux + LUKS servers at Hetzner became unreachable at the same moment. Both had been running for 4+ months without issue. Both had received the same pacman -Syyu the day before, but had stayed on the old kernel until the morning the websites stopped responding. I rebooted — SSH never came back. nmap -Pn -p 22 showed filtered from anywhere. No ping. No banner. The Hetzner Robot panel insisted the hardware was fine.

Several hours went into hypotheses that turned out to be wrong:

• The encryptssh initcpio hook referencing a /usr/lib/initcpio/udev/11-dm-initramfs.rules file that no longer exists. Real bug, no boot impact — the initramfs rebuilds anyway.
• PermitRootLogin no in sshd_config. Real misconfiguration, fixed it, didn’t help. A refusing sshd shows closed, not filtered.
• Predictable interface-naming drift after the systemd 260 upgrade. Patched the .network config to match by MAC. Useful hardening; not the cause.
• Stale GRUB stage1 + core.img in the MBR. Arch never re-runs grub-install after a grub package upgrade. Refreshed it. Still filtered.
• Kernel 7.0.5 regression. Downgraded to 6.18.3, the kernel that had run for 4 months. Still filtered. So the kernel itself wasn’t it either.

The clue was in the persistent journal: a single recorded boot from December 31 to May 12 10:13 UTC, and absolutely nothing after. Every reboot since the upgrade was failing before systemd-journald could flush to disk — so the failure had to be in the initramfs, before the root filesystem was even mounted.

What it almost certainly was

Hetzner Dedicated servers configure the initramfs network with ip=dhcp on the kernel command line. That depends on Hetzner’s DHCP server replying to whatever request format the current kernel sends. Somewhere between kernel 6.18 / iproute2 6.18 and kernel 7.0 / iproute2 7.0, the request format changed enough that Hetzner’s DHCP stopped responding. Effects:

• Old kernel at runtime kept the interface already configured (Phase A — 32 hours of healthy operation after the package upgrade).
• New kernel cold-boots, hits DHCP, never gets an IP, dropbear cannot listen, port 22 stays filtered.

Hetzner’s own documentation has been quietly moving away from ip=dhcp toward static IPv4 in the kernel command line. The fix is exactly that:

One line in /etc/default/grub, grub-mkconfig, reboot. No more dependency on Hetzner’s DHCP responding to whatever your current kernel sends.

Why it matters for anyone running this stack

If you run Arch on Hetzner Dedicated with full-disk encryption and remote unlock via dropbear, the ip=dhcp shipped by installimage is a latent bug. It can keep working for years and then break overnight, on every machine you have, after a routine pacman -Syyu. The static-IP version is what Hetzner now recommends and removes the entire dependency.

Tooling

While debugging, I turned the whole rescue / chroot / diagnose / fix workflow into a Python CLI (hal) — including hal fix static-ip, which derives the static cmdline directly from your existing systemd-networkd .network file:

→ github.com/kevinveenbirkenbach/hetzner-arch-luks

Single command, idempotent, reversible (the original /etc/default/grub is backed up to .hal-backup). If you’re on this stack, switch to static IP before the next kernel upgrade catches you.

At home, on most common network which are statefull #dhcp,

You usually get an #ipv4 based on your hardware MAC address, this ensures constancy across device reboot, dual boot (and distro hoping 🙈)

But #ipv6 do not care about the hardware, it will look for a DUID (small string) at /etc/dhcp/duid.

You can persist this file into your dots for your ipv6 address to survive across OS changes.

#linux #archlinux

@keefeglise

The DHCP server running on that router won't give anyone else that same address whilst it has leased it to your NAS machine.

But it's not actually *static*. It's dynamic. It's just dynamic over and over with *usually* the same result.

It's a convenience feature that the DHCP client and server, after either one has restarted, will attempt to lease the same IP address that was used before. So most people don't experience things shifting a lot, because *usually* this feature keeps the address lease the same as prior to the restart.

@stroz @dzwiedziu @gavin57
#LAN #NetworkAdministration #DHCP