Disabling IPv6 on Debian

Applies to: Medulla 
Version: Debian 12
Environment: On-Premise
Category: Networking / Deployment / IPv6

Background

In certain environments (such as OVH, VPS, NAT, incomplete DNS, or hybrid IPv4/IPv6 networks), IPv6 can cause connectivity or network resolution issues.

It may therefore be necessary to disable IPv6 on the Debian server to ensure stable operation of Medulla.

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Temporarily Disabling IPv6

This method disables IPv6 until the next server reboot.

1. Open an SSH terminal

ssh root@SERVER_IP

2. Disable IPv6

Run the following command:

sysctl -w net.ipv6.conf.all.disable_ipv6=1

3. Verify that IPv6 is disabled

cat /proc/sys/net/ipv6/conf/all/disable_ipv6

Expected result:

1

If the returned value is 1, IPv6 is disabled.

Warning:
Depending on your network configuration, this operation may cause a temporary SSH disconnection.

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Permanently Disabling IPv6

To permanently disable IPv6, you must modify the sysctl configuration.

1. Edit the sysctl file

nano /etc/sysctl.conf

2. Add the following lines to the end of the file

net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default.disable_ipv6 = 1
net.ipv6.conf.lo.disable_ipv6 = 1

3. Apply the configuration

sysctl -p

4. Verify that IPv6 is disabled

cat /proc/sys/net/ipv6/conf/all/disable_ipv6

Expected result:

1

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Network verification

To verify that IPv6 is no longer active:

ip a | grep inet6

No IPv6 addresses should appear (excluding the loopback interface, depending on the configuration).

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Default Values

Element	Value
Temporary Disabling	sysctl -w net.ipv6.conf.all.disable_ipv6=1
Permanent file	/etc/sysctl.conf
Application command	sysctl -p