On 04/07/17 08:17, Rick Stevens wrote:
On 04/06/2017 02:45 PM, Stephen Morris wrote:
> On 4/6/17 9:20 AM, Ed Greshko wrote:
>> On 04/06/17 06:57, Stephen Morris wrote:
>>> Hi Ed, just as a side issue to this, because my ISP (I don't know
>>> about my VPN provider) IPv6 at all for anything, I was setting IPv6 to
>>> 'ignore' via Networkmanager in KDE (Gnome doesn't seem to have
>>> same options) but that was causing messages in the logs at boot time
>>> about IPv6 not being ready. How do we stop the network from attempting
>>> to activate IPv6 and then producing these messages when it has been
>>> turned off?
>> (We inadvertently went off list...So I will reproduce what I sent Steve
>> Early AM here in Taiwan. No coffee yet.
>> I think you are saying your ISP isn't providing IPv6 support at all and
>> that you'd like to totally disable IPv6. If that is the case then you
>> can do this by adding ipv6.disable=1 to the kernel boot parameters in
>> If I misunderstood your question let me know and I'll try again after
>> Later, with still no coffee.....
>> I decided to do a test and add ipv6.disable=1 to the kernel parameter on
>> one of my VM's. In the past, this was sufficient. However, doing only
>> this now results in selinux errors. To avoid those you also need to add
>> "net.ipv6.conf.all.disable_ipv6 = 1" to /etc/sysctl.conf.
> Your assessment was correct Ed. I meant to say that my ISP doesn't
> support IPv6 at all.
> Instead of setting the IPv6 options to 'Ignore' in the networkmanager
> definition for my router, I have set the option to 'Link-local', which
> has also stopped the boot time messages. What exactly does 'Link-local'
> actually do (my assumption was it has activated IPv6 addressing for
> local network routing but not activated IPv6 for internet routing)?
Uhm, sorta. A link-local address means those IPs will only be used
in the local LAN segment and should not attempt to traverse gateways.
Link-local addresses are actual IP addresses. In IPV4, the allowed
addresses are inside the 169.254.1.0 - 169.254.254.255 range (note that
this is almost, but not quite the CIDR 169.254.0.0/16) but are NOT
mandatory. In IPV4, if you have a valid IPV4 address, that's good
enough for everything.
NOTE: The link-local IPV4s look like they're routable since they're not
in the private IP networks 10.0.0.0/8, 172.16.0.0/12 or 192.168.0.0/16.
Since routers will not pass those link-local IPs along, they're really
For IPV6, link-local addresses are in fe80::/10 (to conform to /64
requirements on LAN segments, it's often called fe80::/64) and ARE
mandatory (used for things like DHCPV6 and NDP). Unlike IPV4, IPV6
_requires_ every interface to have (at least) a link-local address. If
the IPV6 interface is externally routable, it will require a second
IPV6 IP which is used for the external routes, so most IPV6 interfaces
you see will have two (or more) addresses associated with them.
Confusing, ain't it? My brain starts to bleed every time I get into this
Another thing worth mentioning. You can use the link-local addresses
within the same LAN segment but you must specify the interface to be used.
[egreshko@meimei ~]$ ping6 fe80::6025:85ec:2615:8969
connect: Invalid argument
[egreshko@meimei ~]$ ping fe80::6025:85ec:2615:8969%enp2s0
56 data bytes
64 bytes from fe80::6025:85ec:2615:8969%enp2s0: icmp_seq=1 ttl=64
64 bytes from fe80::6025:85ec:2615:8969%enp2s0: icmp_seq=2 ttl=64
64 bytes from fe80::6025:85ec:2615:8969%enp2s0: icmp_seq=3 ttl=64
64 bytes from fe80::6025:85ec:2615:8969%enp2s0: icmp_seq=4 ttl=64
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