How to disable ipv6 on a specific interface in linux?

Could someone tell me how to disable ipv6 auto-config on a specific network interface in CentOS?

The current situation is:

A PC has two network adapters eth0 and eth1 that are connecting to the same LAN, in which, IPv6 router is advertising an IPv6 prefix with NDRA (Neighbor Discovery Router Advertisements) packet. As a result, both eth0 and eth1 are configuring the IPv6 address with that prefix automatically.

But, I just want to enable ipv6 on eth1 and disable it on eth0. I've tried the following methods, but they don't work.

1. /etc/sysconfig/network

NETWORKING_IPV6=no
IPV6_AUTOCONF=no

This will disable ipv6 on both eth0 and eth1.

2. /etc/sysconfig/network-scripts/ifcfg-eth0

IPV6INIT=no
IPV6_AUTOCONF=no

Then, it doesn't work. I have restarted the network service already. I am a little confused about this issue. Thanks in advanced.

Yves Messi

Posted 2013-03-30T12:17:19.230

Reputation: 253

sysconfig.txt definitely implies that what you've done should disable IPv6 on a specific interface. However, it seems those flags are ignored. There are two bug reports about this, which were also ignored. See https://bugzilla.redhat.com/show_bug.cgi?id=982740 & https://bugzilla.redhat.com/show_bug.cgi?id=496444

– Stefan Lasiewski – 2017-03-09T21:12:51.137

Answers

You can disable it from /etc/sysctl.conf with this line:

net.ipv6.conf.eth0.disable_ipv6 = 1

Take a look at /proc/sys/net/ipv6/conf/eth0. There are many options you can set in that directory, like leaving IPv6 enabled but disabling autoconf etc.

Sander Steffann

Posted 2013-03-30T12:17:19.230

Reputation: 4 169

4FYI for those looking to disable all, not just one interface, simply replace "eth0" with "all" – Peter – 2015-01-20T10:02:29.863

1Actually, instead of modifying /etc/sysctl.conf, create a file in /etc/sysctl.d named for example 00_ipv6_off.conf with the above contents. ifconfig will then show interfaces bereft of IPv6 functionality. – David Tonhofer – 2018-12-17T13:03:53.887

In one line: echo "net.ipv6.conf.eth0.disable_ipv6 = 1" > /etc/sysctl.d/00_ipv6_off.conf – David Tonhofer – 2019-01-22T16:30:12.207

$ sudo sysctl -w net.ipv6.conf.eth0.disable_ipv6=1

deprecates

# echo 1 > /proc/sys/net/ipv6/conf/eth0/disable_ipv6

In order to ensure that this change persists across reboots, you'll want to add this line to your /etc/sysctl.conf file:

net.ipv6.conf.eth0.disable_ipv6=1

Note that using the /etc/sysconfig/network-scripts/ifcfg-eth0 file is non-portable.

cjac

Posted 2013-03-30T12:17:19.230

Reputation: 211

You should be root to set network parameter below:

echo 1 > /proc/sys/net/ipv6/conf/wlan0/disable_ipv6

mgundes

Posted 2013-03-30T12:17:19.230

Reputation: 41

This will work in installers as well, if a debian installer is getting stuck at detect network settings. Go to console (alt+2), and type this command. Go back to the installer. Press Ctrl+C to exit the detection, and re-initialize the detection of the network. – lsu_guy – 2019-08-04T05:57:10.630

The use of the following variables in ifcfg-eth0 or ifcfg-eth1:

IPV6INIT=no
IPV6_AUTOCONF=no

Should do the trick. To reiterate:

/etc/sysconfig/network

NETWORKING_IPV6=yes
IPV6_AUTOCONF=yes

/etc/sysconfig/network-scripts/ifcfg-eth0

IPV6INIT=no
IPV6_AUTOCONF=no

/etc/sysconfig/network-scripts/ifcfg-eth0

IPV6INIT=yes
IPV6_AUTOCONF=yes

Then make sure you restart the networking service:

% /etc/init.d/network restart

If you run ifconfig you should see inet6 on the ethernet device (either eth0 or eth1) that has ipv6 enabled.

% ifconfig eth0
eth0      Link encap:Ethernet  HWaddr 01:26:BD:85:CA:30  
          inet addr:192.168.1.20  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fe80::226:c7ff:fe85:a720/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:2497072 errors:0 dropped:0 overruns:0 frame:0
          TX packets:2253781 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:2004576667 (1.8 GiB)  TX bytes:1296051472 (1.2 GiB)

slm

Posted 2013-03-30T12:17:19.230

Reputation: 7 449

1Hmmmm, didn't do squat on my system (RH 6.5 X86_64 on a virtualized environment.) Good to know those for those systems where it works, though. – luis.espinal – 2014-09-17T18:39:34.480

Yes, it's a little weird. Setting "net.ipv6.conf.eth0.disable_ipv6 = 1 " is a good solution. Thanks for your answer. – Yves Messi – 2013-04-01T06:10:06.940