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Does macOS use IPv6 by default now?

E

Ethosik

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Original poster
Oct 21, 2009
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I am trying to track down why my Mac Studio is getting an IPv6 address. I do not see that IPv6 address provided by my Ubiquiti Dream Machine, and IPv6 is not enabled either. So what is handing out my IPv6 address?! I do get a valid IPv4 address, but I want to know why my Mac is also getting an IPv6 one.
 
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Ethosik said:
I am trying to track down why my Mac Studio is getting an IPv6 address. I do not see that IPv6 address provided by my Ubiquiti Dream Machine, and IPv6 is not enabled either. So what is handing out my IPv6 address?! I do get a valid IPv4 address, but I want to know why my Mac is also getting an IPv6 one.
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It's probably iCloud Private Relay, if you have that enabled.
 
Ethosik said:
I am trying to track down why my Mac Studio is getting an IPv6 address.
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Where are you seeing this? Why is it a problem? There are some options in network system preferences for configuration. Default seems to be automatic setup.
 
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HDFan said:
Where are you seeing this? Why is it a problem? There are some options in network system preferences for configuration. Default seems to be automatic setup.
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Well my network doesn't have IPv6 configured, my router is not sending out the IPv6 address, so what is sending it to my Mac? I am trying to diagnose an issue with my NAS and it being slow whenever the connection shows an IPv6.

As to where I am seeing it: System Settings, Network, Ethernet, IPv6 address.

Nermal said:
If it helps, your posts in this thread have been made from an IPv4 address. I wonder whether the v6 address you're seeing is local to your network.
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Yeah Spectrum public IP is still IPv4. It's internal to my network that I am seeing IPv6.
 
Ethosik said:
so what is sending it to my Mac? I am trying to diagnose an issue with my NAS and it being slow whenever the connection shows an IPv6.
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Don't understand the sending part. The Mac either sets the IPV6 address automatically, you set it manually or it is Link-Local (not sure I understand that one). If you are using DHCP the address comes from your DHCP server which is a fetch from your Mac to the DHCP server, not a send. That's what happens with my Comcast modem/router.

Are you saying that the NAS is connecting via IPv6 to your Mac? How are you connecting to the NAS - via an SMB share or? Which NAS are you using?
 
On MacOS (and for just about every other OS too) every network interface is given an IPv6 link local address by the OS itself. This is helpful because you can connect devices to each other without using a router. You can recognize that link local address by the FE80::/10 prefix. IPv4 also has this feature, you might have seen that if you connect devices without a router then the OS will give itself a 169.254.0.0/16 address.

On MacOS you cannot disable IPv6 entirely like you can on other systems, but you can at least force it to remain link local in the interface's settings in the System Settings.app. Other devices on the same network can still talk to the Mac though.

If you rely on disabling IPv6 for privacy/safety reasons you'll absolutely need to place the device behind a hardware firewall that blocks IPv6 instead of trying to change the settings on the local device, since there is no global setting to turn it off there.
 
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HDFan said:
Don't understand the sending part. The Mac either sets the IPV6 address automatically, you set it manually or it is Link-Local (not sure I understand that one). If you are using DHCP the address comes from your DHCP server which is a fetch from your Mac to the DHCP server, not a send. That's what happens with my Comcast modem/router.

Are you saying that the NAS is connecting via IPv6 to your Mac? How are you connecting to the NAS - via an SMB share or? Which NAS are you using?
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Something is sending IPv6 to my Mac. As with IPv4 I see my Ubiquiti Dream Machine is sending it that address. My Ubiquiti is my DHCP Server, so I don’t know why you are confused.

My DHCP doesn’t have IPv6 configured but my mac gets sent (or fetched or whatever it’s all the same) an IPv6 address. Why?
 
okkibs said:
On MacOS (and for just about every other OS too) every network interface is given an IPv6 link local address by the OS itself. This is helpful because you can connect devices to each other without using a router. You can recognize that link local address by the FE80::/10 prefix. IPv4 also has this feature, you might have seen that if you connect devices without a router then the OS will give itself a 169.254.0.0/16 address.

On MacOS you cannot disable IPv6 entirely like you can on other systems, but you can at least force it to remain link local in the interface's settings in the System Settings.app. Other devices on the same network can still talk to the Mac though.

If you rely on disabling IPv6 for privacy/safety reasons you'll absolutely need to place the device behind a hardware firewall that blocks IPv6 instead of trying to change the settings on the local device, since there is no global setting to turn it off there.
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But my router doesn’t have IPv6 enabled. Sometimes the connection to my Synology is using the IPv6 address and when this happens I get 100Mbps experience instead of 10Gbps with IPv4. So how can I stop a Mac getting (or fetching whatever it’s all the same) an IPv6 address?
 
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Ethosik said:
But my router doesn’t have IPv6 enabled.
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It doesn't matter, the address comes from the device itself. MacOS does that.

Ethosik said:
So how can I stop a Mac getting (or fetching whatever it’s all the same) an IPv6 address?
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You cannot, MacOS assigns itself an IPv6 address and you can't stop it from doing that. Disable IPv6 on the NAS instead, or connect to it specifically via its IPv4 address instead of the hostname. I guess you could also force it with an entry in the /etc/hosts file.
 
okkibs said:
It doesn't matter, the address comes from the device itself. MacOS does that.


You cannot, MacOS assigns itself an IPv6 address and you can't stop it from doing that. Disable IPv6 on the NAS instead, or connect to it specifically via its IPv4 address instead of the hostname. I guess you could also force it with an entry in the /etc/hosts file.
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That seems dumb. Why does it have one if it can’t be used?
 
okkibs said:
??? It can be used. Again, IPv4 behaves the same way.
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How can it be used if my routers don’t support it? It can’t switch properly and handle the address. This is evident by my absolute poor performance when it gets used for my NAS connection.

My Mac didn’t randomly generate its own IPv4 address. My router did. My router has the setting to provide it a static IP. I can’t use a random IPv4 outside my subnet.
 
svenmany said:
Can you tell us what IPv6 address(es) your Mac has?
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Not sure. I assume it wouldn’t be anything sensitive but if my router isn’t providing it I don’t know how it gets generated. By serial key of product? My public IP?
 
Ethosik said:
Not sure. I assume it wouldn’t be anything sensitive but if my router isn’t providing it I don’t know how it gets generated. By serial key of product? My public IP?
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Sorry, I didn't mean "can you tell us" (my grammar teacher would be pissed). I meant "would you please tell us".

In the terminal type "ifconfig". There might be a bunch of interfaces listed. For me "en0" is my WiFi interface and "en11" is my ethernet interface. I have a number of ethernet interfaces, one for each way I might connect (a different dock, an ethernet dongle).

For the interface that connects to your NAS, take a look at the lines that say inet6. What values are listed? If you're uncomfortable revealing that values, then just tell us if any IPv6 entries don't start with fe80 or are "::1".
 
Which Synology do you have? What firmware? How are you connecting to your Mac? Is "First use IPv4 address to resolve domain name" checked in Network Advanced Settings? Have you turned off IPv6 for the active network interface?
 
svenmany said:
Sorry, I didn't mean "can you tell us" (my grammar teacher would be pissed). I meant "would you please tell us".

In the terminal type "ifconfig". There might be a bunch of interfaces listed. For me "en0" is my WiFi interface and "en11" is my ethernet interface. I have a number of ethernet interfaces, one for each way I might connect (a different dock, an ethernet dongle).

For the interface that connects to your NAS, take a look at the lines that say inet6. What values are listed? If you're uncomfortable revealing that values, then just tell us if any IPv6 entries don't start with fe80 or are "::1".
Click to expand...

IPv6 address starts with fd46

HDFan said:
Which Synology do you have? What firmware? How are you connecting to your Mac? Is "First use IPv4 address to resolve domain name" checked in Network Advanced Settings? Have you turned off IPv6 for the active network interface?
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DS1817+
DSM 7.1.1-42962 Update 6
10Gb connection is with a switch
"First use IPv4 address to resolve domain name" - I do not see this, is this a Mac setting or Synology?
Have you turned off IPv6 for the active network interface - I just turned off IPv6 for the Synology, but want to know why my Mac has an IPv6 address.
 
Ethosik said:
but want to know why my Mac has an IPv6 address.
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All Macs get an IPv6 address and will use it for communication on your LAN. This is not new, it has been true for many years. There is no reason to turn this off.

I don't know why you feel you have a need to turn it off for your Synology. But @HDFan knows better than me if that is desirable.
Ethosik said:
IPv6 address starts with fd46
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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.
 
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gilby101 said:
I don't know why you feel you have a need to turn it off for your Synology.
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He was complaining that the Synology had slow transfer speeds when it was connecting to the Mac via iPv6. Since you can't totally turn off iPv6 on the Mac but can on the Synology ....
 
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gilby101 said:
All Macs get an IPv6 address and will use it for communication on your LAN. This is not new, it has been true for many years. There is no reason to turn this off.
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Right. But if my DHCP doesn't support IPv6, what is the point for a Mac to have one? How does it get one? Why does it communicate with my NAS with one when my DHCP doesn't have IPv6 enabled?

I have never seen this until recently, I have never had this issue until recently. My Windows system does NOT get an IPv6 address by default.
 
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