Why does Mac have 2 WiFi IP addresses?

[donawalt]

As you can see from the arp command shown in the picture in this post, my one MacBook Pro (MAC ending in B5:01) has two IP addresses that it responds to - .74 and .133! There is no hard wired/Ethernet connection. I noticed this through my router's connected device page, the Mac would flip between 2 IP addresses. Both a ping to .74 and .133 work.

Can anyone shed any light on this, and is it possible to have it just respond to 1 IP address? Thanks!

 

[User #07242024]

That’s normal. You can adjust IP by going to Network in System Preferences or System Settings.

 

[xboxbml]

As you can see from the arp command shown in the picture in this post, my one MacBook Pro (MAC ending in B5:01) has two IP addresses that it responds to - .74 and .133! There is no hard wired/Ethernet connection. I noticed this through my router's connected device page, the Mac would flip between 2 IP addresses. Both a ping to .74 and .133 work.

Can anyone shed any light on this, and is it possible to have it just respond to 1 IP address? Thanks!

View attachment 2436772

Maybe cuz you have hide my IP enabled?.. Not sure.. I'd have to do some research on that myself..

 

[xboxbml]

Maybe cuz you have hide my IP enabled?.. Not sure.. I'd have to do some research on that myself..

Well, I don't think that's it.. I have that enabled in safari and I only see 1 IP on my Mac in ifconfig...hmm..

 

[Ruggy]

I think it might be because your router is broadcasting on both 2.4ghz and 5ghz.
You will connect seamlessly from one to the other depending on which has the best signal- 5 will be fastest but have lower penetration and range.

 

[donawalt]

@Ruggy yes but no other Mac in the house does this…same with private IP address, which is actually off everywhere @xboxbml ?

 

[kevcube]

This is something that will only be controlled by the Mac if you have ever configured it to use a static IP. Otherwise this is a decision of your DNS server which is your router's domain.

MacOS has the ability to provide a virtual MAC address and rotate it periodically, which would lead the DNS server to assigning a new IP, but then the MAC would not match in ARP.

I think for some reason your DNS server assigned a new IP to the mac and its cached on the windows machine.

This could possibly be due to it connecting to both 2.4ghz and 5ghz wifi networks.

 

[donawalt]

Thanks @kevcube . I did have a static ip for it, for awhile, but not now. Neither of these ip addresses are the address that it was assigned with a static IP, however. Also, I don’t think it’s the 2.4 and 5 GHz networks, as a test I turned Wi-Fi 6E off, so that it connected to the network via Wi-Fi 5, and it kept the same IP address as it has when it is connected at Wi-Fi 6.

It sounds most likely that the router/dhcp has cached the ip address, especially since none of this set up or configuration I’ve discussed is unique to this Mac, another Mac is exactly the same, and it does not have two IP addresses. So I have to flush the cache on the router probably?

 

[dmccloud]

The first thing I noticed in the OPs screenshot is that they are in a Windows command prompt rather than the Mac Terminal. If you run that command in the Mac Terminal (or even iTerm 2) the output is formatted differently:



This makes me wonder whether the OP is running Windows via Boot Camp on an Intel-based machine or via Parallels on an Apple Silicon machine. My initial guess is via some sort of virtualization given the sheer number of IP addresses listed in the OPs screenshot.

 

[donawalt]

Yes it's a Parallels VM on a MacBook Pro M3. Still shouldn't happen though right?

 

[chabig]

Yes it's a Parallels VM on a MacBook Pro M3

I think this is the answer. If you Parallels network setting is Bridged mode, your Mac and your Windows machine will have distinct IP addresses. But the network will see them both at the same physical address.

https://download.parallels.com/desktop/v18/docs/en_US/Parallels%20Desktop%20User's%20Guide/33015.htm

 

[donawalt]

Ah - I am using Bridged mode (bug in Shared mode that Parallels is working on). So if I want to see this one as 2 unique computers, do I do the "Generate MAC Address" to fix it?

EDIT: MAC addresses are different - the laptop has MAC ending in B5:01, the VM is using F65.

Mac is using 192.168.1.74. Network properties in Windows in the VM is reporting using 192.168.1.75.

Here is what arp -a shows in Mac terminal, since you discovered it's different than in Windows: