Does macOS use IPv6 by default now?

[Ethosik]

fc and fd addresses are Unique Local Addresses. More common are Link Local Addresses which start with fe80. I don't know why you are getting an fd rather than fe80.

You really don't need to worry about it except for (optionally) gaining some understanding of how IPv6 allocates addresses.

Yes I do because I only get 10-30 MB/s transfer speeds whenever the active connection in my NAS is IPv6. Probably because my router and switches don't have IPv6 enabled so it probably messes with the connection.

And if it's a link local address, that is an equivalent of a 169 APIPA IPv4 address which has caused all sorts of issues in the past....like bad network performance.

I really don't understand the push back on this. Bottom line, my network doesn't have IPv6 and every single time my connection to my NAS is IPv6 I get very slow speeds. This is like saying "don't worry about and and look up how IPv4 works when you get a 169 APIPA address". Which clearly means a bad network/internet connection/setup issue.

I really don't understand why it is okay for a Mac to generate this AND communicate with my NAS when my network clearly doesn't have this enabled. It just causes me headache. Luckily HDFan gave me some options to address on the NAS side but macOS should obviously allow you to disable this.

I also opened a support ticket with Synology and they indeed said that would cause performance issues. So thankfully, Synology is the smart one here and I can disable it on that side. But macOS is just dumb to auto-generate an IPv6 address when it cannot be used.

 

[Ethosik]

Synology Network Advanced Settings.

I found it, you didn't mention it was in an odd place in the General tab. I have enabled it now.

 

[svenmany]

I really don't understand the push back on this.

You have a legitimate concern. But, your bothered by the fact that your interface has an IPv6 address; that is a standard, so you'll get pushback. You're real issue is that IPv6 is being used, not that you have an address.

I've never tried it, but there is a terminal command:

sudo networksetup -setv6off networkservice

You would list your network services with

networksetup -listallnetworkservices

About DHCP - in the link I provided earlier, the two approaches to getting IPv6 addresses, SLAAC and DHCPv6, are discussed. MacOS does not use DHCPv6 for IPv6 (or so I've read in an old-ish post). I certainly don't see any way in System Settings to specify DHCPv6. The only choices are:

Automatically - which I believe is SLAAC
Manually - you type your address in
Link-Local Only - you get nothing more than the fe80 address

 

[Ethosik]

You have a legitimate concern. But, your bothered by the fact that your interface has an IPv6 address; that is a standard, so you'll get pushback. You're real issue is that IPv6 is being used, not that you have an address.

I've never tried it, but there is a terminal command:



You would list your network services with



About DHCP - in the link I provided earlier, the two approaches to getting IPv6 addresses, SLAAC and DHCPv6, are discussed. MacOS does not use DHCPv6 for IPv6 (or so I've read in an old-ish post). I certainly don't see any way in System Settings to specify DHCPv6. The only choices are:

Automatically - which I believe is SLAAC
Manually - you type your address in
Link-Local Only - you get nothing more than the fe80 address

And it appears to only be a standard for Macs. My Windows clients don't have IPv6 and my NAS didn't have one either before I just turned it off. So my complaint here is why does Mac have it by default if my network cannot support it? Just like getting an APIPA IP address if you have a bad network setup - a 169 address is not within the subnet mask and IP range of the main network, and it causes issues when Windows generates one. It means there is a problem. But you all are telling me macOS generates one even if there is no problem, and that is an issue. The Synology rep has confirmed this causes an issue, and it is a shame Macs do this.

And it is a wrong thing to push back on instead of "read up on how IPv6 works", to just "Yes its on by default, just disable it" is the solution. As confirmed by Synology rep. And since Macs can't get it disabled, I thankfully had an option in the NAS.

So I essentially got what I asked in this thread. Yes Mac generates an address even if your network doesn't support it. Which is a big issue as like I said my Windows systems do not. And it causes an issue for me so I had to change some settings on my NAS to not allow IPv6.

 

[svenmany]

And it appears to only be a standard for Macs.

I don't have Windows in front of me since I'm sitting in a coffee shop. But, I just now fired up a Linux VM. The network interface got a link local IPv6 address.

And since Macs can't get it disabled, I thankfully had an option in the NAS.

I think the command I told you about disables it on the Mac.

When I get home, I'll check my windows machine. I'd be surprised if it didn't have an IPv6 address. But, surprise is a learning opportunity.

 

[Ethosik]

When I get home, I'll check my windows machine. I'd be surprised if it didn't have an IPv6 address. But, surprise is a learning opportunity.

I have 4 Windows systems and none of them have an IPv6 address.

 

[svenmany]

I have 4 Windows systems and none of them have an IPv6 address.

Thanks for that. I'm looking forward to reviewing my home system.

https://www.windowscentral.com/software-apps/windows-11/how-to-disable-tcpipv6-ipv6-on-windows-11

Here's a quote from that:

On Windows 11, by default, the system uses the Internet Protocol version 6 (TCP/IPv6) and IPv4 protocols in a dual-stack configuration. Although IPv4 is still the primary protocol in local networks, using both versions is a good idea since more and more modern applications depend on the protocol.

 

[Ethosik]

Thanks for that. I'm looking forward to reviewing my home system.

https://www.windowscentral.com/software-apps/windows-11/how-to-disable-tcpipv6-ipv6-on-windows-11

Here's a quote from that:

Could be the 10Gbe NIC I installed that disabled it then. I don't have it.

 

[svenmany]

Interesting. I nagged my friend who is sitting next to me to let me at his computer. Here's what I see on his Windows 10 machine:

 

[Ethosik]

OMG I figured it out. It was just shocking to me why Mac would just have an address when it can't be used. I should have just assumed it was the same as the 169 APIPA like before. Sure enough, stupid Eeros in Bridge Mode was giving out the IPv6 address. I turned those off and now I am not getting one. Time to replace those with Ubiquiti wifi routers then. Strange that it would impact an ethernet connection though. I guess it was still having a fight over DHCP.

 

[Ethosik]

Sure enough. Reconnected Eeros and now I see IPv6 on that page. I also tested my onboard gigabit ethernet on my Windows system, yep it got it too when the Eeros were connected but it did NOT get one when I had the erros offline. So must be my 10Gbe disabled it for Windows, and Eeros would allow an IPv6 address to generate.

I think when the operating system states it supports it by default, means if your network supports it, it will automatically work (as in you don't need to configure anything). I do not think, as my test with Eeros shows, that it would just assign a no-use IPv6 address.

I guess the conflict arises when my Eero and Ubiquiti fight over DHCP I get the IPv6.

And yep, looked at Eero settings and sure enough it has IPv6 enabled (but cannot change it since it is bridge mode....thanks).

 

[svenmany]

I'm glad you got it sorted out.

I found your discovery a bit puzzling, so I investigated a bit and wanted to report what I understand. No need to respond.

System Settings, in the panel you posted, only shows the IPv6 of "global unicast addresses". Also, the WiFi version of this doesn't bother showing any IPv6 addresses. For both types of interfaces, you can always see those types of addresses when you click on "Details..." and look in the "TCP/IP" section. So, if you have a problem in the future and are using WiFi, make sure you check there to be sure you have no such IPv6 address.

In either case, link-local IPv6 addresses seem to never be displayed in System Settings, as far as I can tell. You will always have link-local IPv6 addresses and those addresses will always allow you to communicate with other IPv6 devices on your network. Those address are not given out by any router on your network.

So, if you were to turn on IPv6 on your NAS, your problem could resurface. It's a question of routing priority. Is IPv6 prioritized over IPv4. I did a very quick search and only found one person say that MacOS chooses the lowest cost route. For Windows, Microsoft's website, https://learn.microsoft.com/en-US/troubleshoot/windows-server/networking/configure-ipv6-in-windows, mentions

By default, Windows favors IPv6 global unicast addresses over IPv4 addresses.

However, link-local addresses are not global unicast addresses. They are silent on the priority with respect to link-local addresses.

One last point - System Settings is horribly buggy with respect to networking. As I swapped around my ethernet between VLANs during testing, the settings panel would only partially refresh. It's important to restart System Settings whenever a change is made to ensure you are seeing the correct information.

And that all the news I have that's fit to print.

 

[Ethosik]

System Settings, in the panel you posted, only shows the IPv6 of "global unicast addresses"

Maybe behind the scenes it generates a hidden IPv6 address, but it doesn't display on any of the reports. I did not see an IPv6 listing when I ran a terminal command with the Eero disabled too. Same with Windows, as my screen shot shows not even IPv6 listed there.

Again, could be under the scenes deep in the network stack, but all I care about is user experience here. We both can be right here. Bottom line, the network config page on macOS or terminal commands on Windows/Mac did not show an IPv6 address when I had disconnected the Eero.

The issue is I need to keep my Eeros connected for a bit, I won't be able to replace them for a couple months or so. So I need to find out how to resolve this so I don't have IPv6 conflicts in the future until I get them replaced. Which is weird that it impacts my Ethernet connections. I don't have my Macs connected to wifi anyway.

 

[svenmany]

We both can be right here.

Yeah, I wasn't correcting you. I'm just puzzled.

For me "ifconfig | grep inet6" shows fe80* entries.

The awdl* interface is used for AirDrop. That uses IPv6. I see lots of activity using the IPv6 link local address when I AirDrop between my phone and mac. I believe that if you have no IPv6 addresses then Airdrop would not work for you.

It's a puzzle.

 

[Ethosik]

Yeah, I wasn't correcting you. I'm just puzzled.

For me "ifconfig | grep inet6" shows fe80* entries.

The awdl* interface is used for AirDrop. That uses IPv6. I see lots of activity using the IPv6 link local address when I AirDrop between my phone and mac. I believe that if you have no IPv6 addresses then Airdrop would not work for you.

It's a puzzle.

That could be it since I don't use Airdrop. I do know Apple does a lot of ad-hoc connections so that must be at play here. Maybe it's a wifi only thing? Since I use Ethernet on my desktop Macs and disable Wifi that might explain it.

 

[bogdanw]

I've never tried it, but there is a terminal command:
sudo networksetup -setv6off networkservice

I always use it, sudo is not required in current macOS versions.

networksetup -setv6off Wi-Fi

networksetup -setv6off Ethernet

I also have IPv6 disabled in my router.

 

[mrkapqa]

on the macpro you would use

networksetup -setv6off Ethernet\ 1
networksetup -setv6off Ethernet\ 2

How to disable IPv6 on Mac - 3 verified methods

This short article explains how to disable IPv6 on Mac and presents alternative solutions for the case when the turn off IPv6 option is not available.

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