CentOS - Sep 2006 - Disabling IPv6 in Centos 4.x Experiences

Hi there,

While I was looking "how to disable ipv6 under centos" I have found a
gazzillion pages about how to do it and some of then even list things that i
am not sure where they came from, so for the record I list most of them here
in case someone else need them.
Some of the methods involved the direct modification of system scripts, and
I am against that so I wont list them here (removing the entire section of
ipv6 calls in IFUP is not a good idea).

How to disable ipv6 support in Centos 4.x
Pick any method, a combo or all of them

Method 1, add the line:
alias net-pf-10 off
to the /etc/modprobe.conf

Method 2 Add to /etc/sysconfig/network file:
NOZEROCONF=yes      # Bonus: Disable the ugly generation of 169.254 zeroconf
networks.
NETWORKING_IPV6=no

Note about method 2. I must mention the fact that I actually READ the entire
ifup script and dependencies and I found that it calls at line 361:
#   if [ "${NETWORKING_IPV6}" = "yes" ]; then
#          /etc/sysconfig/network-scripts/ifup-ipv6 ${CONFIG}

However adding the NETWORKING_IPV6=NO has no effect whatsoever because even
after a reboot the interfaces continue to load an ipv6 address. BTW it does
the same for zeroconf and doesn`t work either.

Method 3:
/etc/sysconfig/network-scripts/ifcfg-XXXXX file;
IPV6INIT=no


So pick your best method or a combo and let us know which one worked for
you:
In my case Centos 4.3 2.6.9-34.EL i386 with a pair of 3COM 3c905CX lan
boards did not responded to Method 1 and 2 and 3. So I'm still battling with
this ipv6 thing.

Let me know your comments.

Cheers,




-- 
------------------------------------------------------------
Erick Perez
Panama Sistemas
Integradores de Telefonia IP y Soluciones Para Centros de Datos
Panama, Republica de Panama
Cel Panama. +(507) 6694-4780
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> Hi there,
>
> While I was looking "how to disable ipv6 under centos" I have
found a
> gazzillion pages about how to do it and some of then even list things that
i
> am not sure where they came from, so for the record I list most of them
here
> in case someone else need them.
> Some of the methods involved the direct modification of system scripts, and
> I am against that so I wont list them here (removing the entire section of
> ipv6 calls in IFUP is not a good idea).
>
> How to disable ipv6 support in Centos 4.x
> Pick any method, a combo or all of them
>
> Method 1, add the line:
> alias net-pf-10 off
> to the /etc/modprobe.conf
I use method 1 successfully.

Erick Perez wrote:
> Method 1, add the line:
> alias net-pf-10 off
> to the /etc/modprobe.conf
This is the right way to do it.
> Method 2 Add to /etc/sysconfig/network file:
> NOZEROCONF=yes      # Bonus: Disable the ugly generation of 169.254 
> zeroconf networks.
> NETWORKING_IPV6=no
> 
> However adding the NETWORKING_IPV6=NO has no effect whatsoever because 
> even after a reboot the interfaces continue to load an ipv6 address. BTW 
> it does the same for zeroconf and doesn`t work either.
It doesn't work on its own since as soon as first IPv6-capable daemon 
(for example sshd) attempts to bind to the ports, the ipv6 kernel module 
gets loaded and it will assign all interfaces default link local 
addresses to all interfaces.

However, do note that apart from deleting ipv6.ko from the disk, there's 
no good way to get rid of IPv6 for sure.  Even with the both of the 
above, if somebody/something does "modprobe ipv6", the module gets 
loaded and it does its thing with link local addresses.  Once it is 
loaded it is next to impossible to unload it from the running system.