debian – Why is IPv6 disabled upon reboot even after configuring sysctl.conf?


First of all it cracks me up how many articles are out there to force IPv6 OFF on linux servers. Come on folks, get with the new! 😀

root@hodor:~# lsb_release -a
No LSB modules are available.
Distributor ID: Debian
Description:    Debian GNU/Linux 10 (buster)
Release:        10
Codename:       buster
root@hodor:~# uname -a
Linux hodor 4.19.0-8-amd64 #1 SMP Debian 4.19.98-1 (2020-01-26) x86_64 GNU/Linux

I have a repeatable problem where, after a reboot, one of my bridge interfaces and all child / slave interfaces for that bridge have IPv6 disabled. This causes a failure in setting ipv6 address on the host among other things. This is what I see

net.ipv6.conf.br0.disable_ipv6 = 1
net.ipv6.conf.enp175s0f0.disable_ipv6 = 1
net.ipv6.conf.enp175s0f1.disable_ipv6 = 1
net.ipv6.conf.hostveth0.disable_ipv6 = 1

I couldn’t find anything of relevance in /etc/sysctl.d/* . Here is my sysctl.conf:

root@hodor:~# grep -v ^# /etc/sysctl.conf






net.ipv4.ip_forward=1

net.ipv6.conf.all.forwarding=1



net.ipv6.conf.br0.disable_ipv6 = 0
net.ipv6.conf.br0/5.disable_ipv6 = 0
net.ipv6.conf.br0/90.disable_ipv6 = 0
net.ipv6.conf.enp175s0f0.disable_ipv6 = 0
net.ipv6.conf.enp175s0f1.disable_ipv6 = 0
net.ipv6.conf.hostveth0.disable_ipv6 = 0
net.ipv6.conf.lo.disable_ipv6 = 0
net.ipv6.conf.all.disable_ipv6 = 0

After I sysctl -p I can then manually set my ipv6 and fix all the other little nuances, but that sucks.

Also thought that maybe grub was my culprit, but I see nothing that refers to this kernel parameter.

root@hodor:~# grep -v ^# /etc/default/grub

GRUB_DEFAULT=0
GRUB_TIMEOUT=1
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX_DEFAULT=""
GRUB_CMDLINE_LINUX="console=tty1 console=ttyS0,115200 intel_iommu=on"
GRUB_TERMINAL="console serial"
GRUB_SERIAL_COMMAND="serial --speed=115200 --unit=0 --word=8 --parity=no --stop=1"

Hopefully this is an easy one. Please help if you can!