[CentOS] Disabling IPv4

Robert Moskowitz rgm at htt-consult.com
Tue Aug 19 13:09:21 UTC 2008


Barry Brimer wrote:
> On Mon, 18 Aug 2008, Robert Moskowitz wrote:
>> Barry Brimer wrote:
>>> On Mon, 18 Aug 2008, Robert Moskowitz wrote:
>>>> Barry Brimer wrote:
>>>>> Quoting Robert Moskowitz <rgm at htt-consult.com>:
>>>>>> I want to seriously work with IPv6 and not have stray IPv4 functions
>>>>>> messing with me.
>>>>>> So in /etc/sysconfig/network, I commented out NETWORKING=yes. I have
>>>>>> NETWORKING_IPV6=yes.
>>>>>> In /etc/sysconfig/network-scripts I altered ifcfg-eth0, setting
>>>>>> BOOTPROTO=none. That was enough for eth0 to only have IPv6 
>>>>>> working on
>>>>>> it (have IPV6INIT=yes and IPV6_AUTOCONF=yes).
>>>>>> But lo had IPv4. So I commented out all of the IPV4 lines in 
>>>>>> ifcfg-lo.
>>>>>> Still have IPv4 on lo. How do I disable that?
>>>>> Try adding "alias net-pf-2 off" to your /etc/modprobe.conf
>>>> I did that and rebooted.
>>>> Then did a ifconfig and lo is still showing an inet address of 
>>>> and I can ping
>>>> So that tends to imply that ipv4 is still running.
>>> I would agree with you.
>>> Have you tried setting ONBOOT=no in 
>>> /etc/sysconfig/network-scripts/ifcfg-lo ??
>> No, but I do want iPv6 loopback, so I need something working for 
>> ifcfg-lo
>> Will try some more tomorrow....
> Maybe you can try removing IPADDR and NETMASK and adding:
> IPV6INIT=yes
> IPV6ADDR=::1
> The complete documentation for the ifcfg files is in :
> /usr/share/doc/initscripts-*/sysconfig.txt
> There is a log of other documentation in this file as well .. I would 
> just search for ifcfg once inside the file.
I am familiar with sysconfig.txt file, and used it to get to where I was....

Edited ifcfg-lo (already commented out all the IPv4 address lines, and 
still was getting, added the onboot=no and the IPv6 commands, 
restarted network and got the message:

RTNETLINK answers: File exists

I rebooted and saw this message when the loopback was brought up (even 
with the onboot=no command!). I disabled iptables (it started before 
loopback). Still betting ipv4.

Started looking through /var/log/messages and see that there is a line:

kernel: NET: Registered protocol family 2

Hey, wait a minute, I have in my /etc/modprobe.conf: alias net-pf-2 off


I also see messages about starting IPv6 over IPv4 tunneling driver. Why? 
I don't need it here for this test?

So it looks like there is a BUNCH of network stuff that runs even if you 
don't ask for it (great defaults, I guess), and no documentation on 
turning the stuff off.....

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