[CentOS] IPv6 broken on Linode

[Alice Wonder]

On 02/16/2017 02:03 AM, James Hogarth wrote:
> On 16 February 2017 at 09:09, Alice Wonder <alice at domblogger.net> wrote:
>> On 02/16/2017 12:54 AM, Tony Mountifield wrote:
>>>
>>> In article <4cbb9dc4-f063-3434-b7a1-d4d0e6581b5e at domblogger.net>,
>>> Alice Wonder <alice at domblogger.net> wrote:
>>>>
>>>> https://forum.linode.com/viewtopic.php?f=19&t=14570&p=72785
>>>>
>>>> I can not figure out what I need to do.
>>>>
>>>> Apparently according to linode support, the VM is trying to grab an IPv6
>>>> address with some privacy stuff enabled by default causing it to not
>>>> grab the IPv6 address that is assigned to me.
>>>
>>>
>>> Does the accepted answer at the following link give you any useful hints?
>>>
>>>
>>> http://superuser.com/questions/243669/how-to-avoid-exposing-my-mac-address-when-using-ipv6
>>>
>>> Cheers
>>> Tony
>>>
>>
>> Not really - I tried
>>
>> net.ipv6.conf.all.use_tempaddr = 0
>>
>> and it still fails to grab the proper IPv6
>>
>> -=-
>>
>> Just in case, I did ask Linode support to verify that my hardware address is
>> what it is suppose to be. Still waiting to hear on that.
>>
>> _______________________________________________
>
>
> it still is key=value  ... it uses the ifcfg- files (via the rh
> plugin) and they are all key=value
>
> It would be helpful if you could paste the journal output (journalctl
> -u NetworkManager) from the time period of attempting to get an
> address ...
>
> also the nmcli conn sh <connection_name> information for the interface
> along with your ifcfg- files

ifcfg-lo is the only one that exists on any of the servers - including 
the VMs that grab the correct IPv6 address.

from /sbin/ifconfig -a :

eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
         inet 178.79.185.217  netmask 255.255.255.0  broadcast 
178.79.185.255
         inet6 fe80::a8ad:d312:4ef4:7272  prefixlen 64  scopeid 0x20<link>
         inet6 2a01:7e00::825f:e564:ad53:72fc  prefixlen 64  scopeid 
0x0<global>
         ether f2:3c:91:18:8a:7e  txqueuelen 1000  (Ethernet)
         RX packets 9903  bytes 1088621 (1.0 MiB)
         RX errors 0  dropped 0  overruns 0  frame 0
         TX packets 7786  bytes 1087223 (1.0 MiB)
         TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

That hardware address - the 18:8a:7e corresponds with what the IPv6 
address is suppose to be. But that's not the address it is grabbing, 
despite the fact that net.ipv6.conf.all.use_tempaddr = 0 is set.

I'm seriously wondering if the real issue is a mis-configured dhcp 
server in their London facility because nothing makes sense.

journalctl -u NetworkManager

reports no journal entries found.

I think the problem must be on their end.

It all was working fine until they migrated the VM because of a hardware 
issue, and I suspect now all the hardware address privacy stuff being 
the issue is barking up the wrong tree because all the reading I have 
done seems to indicate that with

net.ipv6.conf.all.use_tempaddr = 0

that a fake temporary hardware address would not be sent to their dhcp 
server when obtaining the address, but the real one, that should be 
fetching my assigned address.

It's all very frustrating but I suspect now the problem isn't the CentOS 
network configuration.

Five other servers all configured the same (started from same CentOS 7 
image and network stuff left alone) work properly - so I don't know.