If you install a compatible macOS on a new volume of your built-in startup disk, your Mac can start up from either volume. It's an easy way to use a newer macOS while keeping a previously installed macOS for software that might require it.
There are alternatives: If wiping your Mac sounds like too much hassle to you, you could try installing the alternate version of macOS on an external hard drive instead. We show you how here: How to run macOS from an external hard drive.
Two For Mac
So, you want to run two versions of the macOS operating system on your Mac. Your method will depend on which version of macOS you are already running. If you are running High Sierra on an SSD, or have Big Sur, Mojave or Catalina installed, this process is much easier because your Mac will be using the Apple File System APFS.
We ran the macOS Mojave beta on our second volume in 2018-2019, so when we were ready to update to the Catalina beta in 2019 all we needed to do was go to System Preferences and click on Software Update. The Catalina beta was there for us to download (although we did have to update to Mojave beta 10 first).
Having created your second volume using the guide above, you will be ready to install your second version of macOS. This time we are looking at a full version of the operating system, rather than a beta.
We also have advice about downloading older versions of macOS here. For OS options beyond macOS, you might like to read our guides showing How to install Windows on a Mac, and How to install Linux on a Mac.)
The MAC address is tied to the Network Interface Controller (NIC), a subcomponent of the larger device. The NIC is where you make your physical connection to the network, by plugging in an Ethernet cable or connecting to a WiFi signal.
Yes. For each network interface in your device, there is a unique MAC address associated with it. So if your laptop has both an Ethernet port and Wi-Fi built-in, you will see two MAC addresses in the system configuration.
In general, you will find MAC addresses in the system settings, general information, or network settings/status of your device. Occasionally, the MAC address is printed on a label affixed to the bottom of a device.
Speaking in automobile terms, MAC addresses are like Vehicle Identification Numbers (VINs), which are unique to each vehicle. IP addresses are like license plates, which can be reassigned or transferred to different vehicles (VINs).
And moreover when I use Wireshark I do get the error "duplicate IP address detected". Both the machines are sending "I have IP address X" (and mention their own MAC along with) so why is it not two MAC mapping to one IP? What am I missing here?
The answer is correct. When ARP poisoning happens, the attacker machine is saying "Hi, I am 10.20.30.40, my MAC is AABBCCDDEEFF". And the victim machine is saying "Hi, I am 10.20.30.40, my MAC is 112233445566".
Two machines with the same MAC. Why? It's because on the Ethernet layer, IP does not mean anything. The MAC is the address used to route the packet. And when someone needs to send a packet to 10.20.30.40, it's the MAC address that defines who will receive the packet, not the IP. if the MAC is already cached, the packet is sent right away.
You are seeing those "duplicate IP address detected" because 2 (or more) MAC addresses are replying to the same IP. When a message ARP Request: who is 10.20.30.40? Tell 10.20.30.200 is sent, both the attacker and the victim are telling they own that IP, and giving their own MAC addresses.
You're right: narrowly speaking, to perform ARP spoofing is to provoke confusion between one IP address and two MAC addresses. But there are two related terms here that are being conflated: ARP spoofing and ARP collision.
ARP spoofing has more to do with situation and intent: it's an attempt to use ARP to get packets delivered to a destination the network administrator didn't intend. The result will usually be ARP collisions. But since "spoofing" describes a situation, rather than an event, it's likely that there will also be one MAC address with two IP addresses:
Finally, a side note: multiple IP addresses can be legitimately mapped to the same MAC address. In fact, this is standard practice in IPv6, where a server may have both an auto-generated IP address and an administrator-assigned one, both mapping to the same MAC address. Even in IPv4, this can be useful: in a small network without DNS, you could have an existing server "A" take over for another server "B" by shutting down B and giving its IP address to A as a secondary address. This may be preferable to reconfiguring a large number of clients to point to server A's primary address.
This may simply be a misconfiguration. Both devices could have the same IP address configured and as such no ARP spoofing is taking place. This would simply be an IP conflict, which does create issues but can't be called ARP spoofing.
This is common in many networks as a single interface can have multiple IP addresses. With IPv6 in use, a device should have multiple addresses (at least a global and a link local). Dual stack devices should have both an IPv4 address and multiple IPv6 addresses.
On top of that, there are many reasons/devices where more than one IP address are assigned to a single interface. Just as one example among many, load balancers are typically configured to provide services for a number of different IP addresses on a single interface. There are many more examples, but in all these cases, no ARP spoofing it taking place as the devices are using each IP address.
However, this doesn't mean that ARP spoofing is always a negative. An example of a legitimate use of ARP spoofing would be "proxy ARP." One way this can be used is in configurations where direct client-to-client communications is prohibited and must pass through some "central" device where things like security rules may be enforced.
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This question (and others) is driving me nuts and I apologize because it is so basic. Do you know why there are two MAC addresses in iPad's interface table? Only the first digit is changed from a 4 to a 6. MAC address sites recognize one and not the other.
I am trying to figure out if I have been networked into a neighbor's security/surveillance system and thus mapping out what is linking to what. I am using IT tools app as well as searching many websites.
Yep, I confirm, as an owner of both an iPhone and an iPad - they both have 2 MACs, one for Bluetooth, another for WiFi. Furthermore, if you open the Settings app on your device, and go to General -> About, then scroll all the way down, you will see two entries: "Wi-Fi Address" and "Bluetooth" that can help you identify which MAC belongs to which interface.
When I first bought my instant pot mini, I thought I would only use it in the winter for comforting soups and stews. I thought of it as a replacement for my slow cooker. But I was so wrong about that!
I adapted the recipe from Epicurious, and it has a slightly strange method to it: the noodles are cooked in broth and butter at high pressure for 5 minutes, and then the rest is stirred in and allowed to melt slowly.
I happen to love this method, because as the pot comes to pressure, it gives me plenty of time to grate cheese and measure everything out. When the timer goes off, I do a forced pressure release, and dump everything in and walk away.
This instant pot mac and cheese recipe makes about 2-3 big bowls of macaroni and cheese. For my family of 3, we use it as a side dish two nights in a row. (My toddler hardly eats more than 5 of 6 bites of anything). We occasionally enjoy it alone with a salad and a glass of white wine! Or, sometimes we pick up barbecue from our favorite place and use this as a side dish.
For those wondering, I haven't tried to scale up this recipe for anything larger than my 3-quart Instant Pot Mini. Small-batch recipes are what I do on this site, but if you double the recipe succesfully, please let us all know; I'd love to hear about it in the comments section below! (You can also check the full-size recipe on Epicurious, from which I scaled this one down for help).
Hi, I'm Christina! I'm the author of 4 cookbooks all about cooking and baking for two. I have scaled down hundreds of recipes into smaller servings so you can enjoy your favorite dishes without the leftovers! Valentine's Day is my favorite holiday.
How you sync files partly depends on what you are using to work on the files in question. When collaborating with colleagues, they or you might prefer to use Microsoft Office 365 and Google Docs. Therefore, syncing files doesn't require native Apple systems or software. To access those files, you need to log in to your relevant Google or Microsoft account, which can be done in the cloud through a web browser or app. 2ff7e9595c
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