39

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.

ZygD
  • 2,577
Yves Messi
  • 503

6 Answers6

50

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
  • 4,802
19

Let the interface name be stored in the iface variable (must be adapted to your situation) :

$ iface=eth0

Then the command is :

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

deprecates

# echo 1 > /proc/sys/net/ipv6/conf/$iface/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.$iface.disable_ipv6=1

To check if the change was kept (especially after reboot) :

$ sysctl -n net.ipv6.conf.$iface.disable_ipv6
1
SebMa
  • 2,035
cjac
  • 290
12

One way to temporally remove the ipv6 on an interface is: (it will come back after reboot)

ip -6 addr flush eth0

lepe
  • 798
  • 9
  • 17
4

You should be root to set network parameter below:

echo 1 > /proc/sys/net/ipv6/conf/wlan0/disable_ipv6
mgundes
  • 41
  • 1
3

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
  • 10,859
0

sudo vi /etc/modprobe.d/ipv6.conf

# add following line 
options ipv6 disable=1

sudo reboot

Cristian Florescu
  • 291