Looks like no one’s replied in a while. To start the conversation again, simply ask a new question.

User profile for user: B-Spoke
B-Spoke Author
User level: Level 1
18 points

Mac using wrong IPv6 address

I've had a dual stack home network running successfully for several weeks. My home network has a number of Macs and PCs as well as other devices (iPads, Nest products). A couple of days ago, my Mac Pro running El Capitan, could no longer connect to IPv6 sites. I had thought that it was an issue with my gateway, but it was functioning perfectly. On closer review, I noticed that the Mac had decided to create its own IPv6 address using the proper IPv6 prefix. This address does not correspond to the DHCPv6 broadcasts so the Mac cannot connect to the internet via IPv6. Looking through the settings, the Mac has "created" a number of IPv6 addresses with one address being the one sent to it via DHCPv6.


My question is why has the Mac suddenly decided to use its made up IPv6 instead of the DHCPv6 address it has received from the gateway? Since the DHCPv6 address is in its list of IPv6 addresses and that address corresponds to the one assigned by the gateway, I know that the router advertisements are working and the Mac is receiving them. So this is an issue with the Mac settings. The only way to get it to connect via IPv6 is for me to manually enter the correct IPv6 address. The other devices have no issue connecting via IPv6 (PCs & Nest). I would love to delete the other useless IPv6 addresses or tell the Mac to get IPv6 via DHCPv6 and not SLAAC (which is useless on a network where you need specific firewall rules for servers and other specialty devices).

Mac Pro & Mac Mini

Posted on Jan 20, 2018 1:03 PM

Reply
Question marked as Top-ranking reply
User profile for user: B-Spoke
B-Spoke Author
User level: Level 1
18 points

Posted on Jan 23, 2018 8:58 AM

I found a solution/work around.


Login as root and go to the command line. Then manually delete the two link-local (unused) IPv6 addresses by using ifconfig as follows:
ifconfig "interface" inet6 "link-local address"/64 delete


Doing this bumps the global IPv6 to the top of the list and now my Mac connects via IPv6 using the address assigned by the DHCPv6 server. The Mac, of course, regenerates the link-local addresses but they are listed below the global IPv6 address.


My guess is that the computer will "play smart" and wipe this out upon reboot, but at least it gets around the bizarre IPv6 behaviour. Too bad there is no terminal command on the iPad.


This would be a whole lot easier if Apple simply allowed one to delete or prioritise the IPv6 addresses listed in the Network settings. I can delete the interface but I cannot delete the generated link-local addresses? Very strange...

View in context
3 replies
Sort By: 
Question marked as Top-ranking reply
User profile for user: B-Spoke
B-Spoke Author
User level: Level 1
18 points

Jan 23, 2018 8:58 AM in response to B-Spoke

I found a solution/work around.


Login as root and go to the command line. Then manually delete the two link-local (unused) IPv6 addresses by using ifconfig as follows:
ifconfig "interface" inet6 "link-local address"/64 delete


Doing this bumps the global IPv6 to the top of the list and now my Mac connects via IPv6 using the address assigned by the DHCPv6 server. The Mac, of course, regenerates the link-local addresses but they are listed below the global IPv6 address.


My guess is that the computer will "play smart" and wipe this out upon reboot, but at least it gets around the bizarre IPv6 behaviour. Too bad there is no terminal command on the iPad.


This would be a whole lot easier if Apple simply allowed one to delete or prioritise the IPv6 addresses listed in the Network settings. I can delete the interface but I cannot delete the generated link-local addresses? Very strange...

Reply
User profile for user: Grant Bennet-Alder
Grant Bennet-Alder
User level: Level 10
135,505 points

Jan 20, 2018 3:03 PM in response to B-Spoke

As far as I know IPv6 is fully implemented and working on Macs. So this should not be some sort of pervasive issue.


That said, wonky things DO happen, on both IPv4 and IPv6. Many devices have a way of holding onto their previously-assigned IP addresses that seems to contradict "the way it is supposed to work". When that works, great. When that fails, we tend to just fix the narrow problem and move on.


Since the numbers in use on a typical Home network behind a Router are "strictly-local" anyway, most users are just sticking with the more familiar (but no less wonky) IPv4.


--------

One of the most annoying issues that continues to confound me is that you can make changes in the network panes, and think they "took". when they are reflected there. But unless/until you close the window and click (apply), it does not change the operating mode.

Reply
User profile for user: B-Spoke
B-Spoke Author
User level: Level 1
18 points

Jan 22, 2018 9:04 AM in response to Grant Bennet-Alder

Thanks for the reply Grant.


My network is dual-stack so it does not prevent me from accessing the internet, just from accessing IPv6 sites. Unless I use another computer or device to do so.


Interestingly, my old Time Capsule acquired the assigned IPv6 address flawlessly and is now accessible via IPv6 on my LAN (it can also access the internet via IPv6). However, it seems that the iPads and my iPhone are plagued by the same configuration issue that my Mac Pro has, all have globally assigned IPv6 addresses but prefer to use link-local.


The only way I could get the Network Preferences to act half intelligently was to delete the location and create a new one. After doing this about 15 times, my Mac Pro correctly selected the assigned IPv6 address. When I rebooted, it went back to its favourite link-local.


Very bizarre considering these Apple products were all working flawlessly up to a few days ago when they all decided to no longer use IPv6. I've not changed any settings on my gateway and it has had no updates applied in about 1.5 months.

Reply

Mac using wrong IPv6 address

Welcome to Apple Support Community
A forum where Apple customers help each other with their products. Get started with your Apple Account.
Learn more Sign up