Networking problem

[Tom H]

On Thu, May 19, 2011 at 10:06 PM, JD <jd1008 at gmail.com> wrote:
> On 05/19/11 18:45, Tom H wrote:
>> On Thu, May 19, 2011 at 8:57 PM, JD<jd1008 at gmail.com>  wrote:
>>> On 05/19/11 17:41, Tom H wrote:
>>>>
>>>> To the OP: Do you have a "/etc/sysconfig/network-scripts/ifcfg-wlan0"
>>>> and a "/etc/sysconfig/network-scripts/ifcfg-wlan0:0"? What are their
>>>> contents?
>>> I have no  /etc/sysconfig/network-scripts/ifcfg-wlan0:0
>>>
>>> $ cat /etc/sysconfig/network-scripts/ifcfg-wlan0:
>>> DEVICE=wlan0:0
>>> IPV6INIT=no
>>
>> Why do you have "DEVICE=wlan0:0" in
>> "/etc/sysconfig/network-scripts/ifcfg-wlan0"?
>
> I think that is a remnant. Thank for pointing it out.
> I had completely overlooked it. But, it is nevertheless,
> harmless.

You're welcome. It's harmless in your case, except for the weird
ifconfig and netstat outputs. If you were using dhcp, it'd be even
more harmless (only wlan0 would be brought up with a dhcp ipv4 address
and a link-local ipv6 address) or harmful (neither wlan0 nor wlan0:0
would be brought up).


>>>>> It is a valid IPv6 interface.
>>>> It's valid but it isn't routable. It's the equivalent of an ipv4
>>>> 169.254.x.y address.
>>>
>>> Yes. ifconfig always prints this even when ip6 is disabled.
>>
>> No, if ipv6 is disabled, no ipv6 address is assigned to any interface.
>
> I do not see in any of my conf files, nor in services
> where I have enabled ipv6.

Take a look at "CONFIG_IPV6" in "/boot/config...".


> But I think there are other internal interfaces/modules that, [do
> not/are not configured to]
> go out over the LAN, that use ipv6: such as:
> bridge,ah6,esp6,xfrm6_mode_beet,xfrm6_mode_tunnel,ipcomp6,xfrm6_tunnel,tunnel6
>
> But I see your point because I thought that it was completely disabled.
> Now I wonder if any of the loadable modules that get loaded, depend on.
> ipv6 being enabled.
>>>>>
>>>>> The fact that IPv6 layer was disabled on the subnet (as JD clarified it later),
>>>>> does not change anything. Once again, the type of configured interface wlan0
>>>>> is of interest to me, that is IPv6-type.
>>>>
>>>> Since wlan0:0 has a ipv6 address, ipv6 must not be disabled.
>>>
>>> It really IS disabled. Look at the contents of my ifcfg-wlan0 above.
>>> It says IPV6INIT=no
>>
>> "IPV6INIT=no" doesn't disable ipv6; it's used by
>> "/etc/sysconfig/network-scripts/ifup-ipv6" to determine whether to
>> configure ipv6 for that interface. If ipv6.ko isn't prevented from
>> loading through "/etc/modprobe.conf" or a conf file in
>> "/etc/modprobe.conf.d/", an interface will be assigned an fe80 ipv6
>> address.
>
> Correct. I had overlooked that altogether.
> As I asked above, I wonder if some service will break
> if I black list the ipv6 modules.

No idea but possible; exim (on Debian, never tried it on Fedora) craps
out if you disable ipv6 globally without disabling ipv6 in exim's own
configuration.