Wifi mac address is changing

What can cause a MAC Address to change?

It looks like Amazon don’t allow you to choose a specific MAC address but instead allocate you one on machine creation.

Nope, joining to a new network won’t give you a new address.
Installing a new device, won’t change the existing MAC address on your other card.
It’ll, it is a single ’emulated’ network device.

The only thing that can more likely to change your address is a driver update which happened to me many times during the past. When I have an older card, and the manufacturer got sold, or someone bought the company . something like that, THAT part of the MAC address will change when I install a new driver. http://en.wikipedia.org/wiki/MAC_address (The first 3 bytes.)

I just found out when my brother was whitelisting the device MAC addresses that my machines MAC address had changed, so I investigated and found in my WiFi settings «Random hardware address», and it seems it was changing my machines Physical Address everytime I connect to the WiFi. I had to disable it since, we we’re whitelisting the machine’s address. Random hardware address

Encouraging this comment to move up the ranks a bit. This question is very old and since its publication, many vendors have added the randomization feature. Your device may connect with a randomized address and the easiest way to tell is if the second character is a 2, 6, A, or E. Your device may use the same randomized address for a long time or change daily.

A MAC address is the physical address of the layer two medium, and in general will remain with the hardware it is allocated to — in a physical nic, it resides in the firmware or flash on the nic. MAC addresses can be spoofed such as with macchanger on linux so as usual, nothing is concrete. They can also be altered in flash — in some cases fairly easily. However, as the MAC address is bound to hardware, the MAC address changes with hardware changes, not with network changes.

In the case of virtual hardware, it is largely the same deal, except the allocation of a mac address is up to the host, effectively it «creates» the nic that is given to the guest, and so seeing as none of it is real, the mac is made up, and can be changed at any time. It rarely is however. A mac address remaining static is good for virtual platform providers as they can measure all sorts of things based on mac, and of course, allocating IP addresses.

In order to have fixed MAC address in AWS EC2, you can use an EC2 instance in a VPC and attach an Elastic Network Interface to it. ENI is like an additional network card that have fixed IP address (internal and external) and fixed MAC address.

No it doesn’t. The MAC address of a NIC will never change. Once you are in a network it uses RARP to get its logical address from the network.

Now say you install a new NIC and join a network (say the Internet). Each card will get their unique IPs provided by the ISP.

So NIC-1 will mind its business and would not interfere with NIC-2 and NIC-2 would do the same. This is true for any number of NICs, irrespective of the medium. They all have their own MAC addresses and hence would acquire unique logical addresses.

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How to stop MAC address from changing after disconnecting?

Solution 1: Poking around on google there are a lot of other folks with this problem (MAC address is re-generated on wifi/phone resets). Normally a MAC address is burned into the WiFi device.

MAC address keeps changing

Poking around on google there are a lot of other folks with this problem (MAC address is re-generated on wifi/phone resets). It seems to mostly be Motorola hardware.

Normally a MAC address is burned into the WiFi device. So it seems very, very odd to generate MAC addresses on the fly like this. Too much software (technically incorrectly) relies on MAC addresses as a stable identifier for an endpoint, so this seems likely to cause more problems than it fixes.

Here’s a post about the problem from 2010: https://supportforums.motorola.com/thread/38758

The only useful recommendation I saw on the internet was the obtuse ‘WiFi Fixer’ app, that is known to work around some problems on early Android wifi handsets. I saw no concrete evidence that it ‘fixes’ this problem.

Alternatively, you could look into the tools for MAC spoofing (AFAICT, these all require a rooted phone). Then just «spoof» a stable address all the time. Here’s a highly manual method: http://blog.thecodecracker.com/hacks/spoof-mac-address-in-android/

Maybe this will help some lost soul in the future. It turns out, that in the WiFi advanced options (next to proxy and DHCP options) there’s now a feature that randomizes the MAC address (enabled by default. ).

If I only knew this, before I lost so much time diagnosing my WiFi setup.

Did you know that you can long press the connection? It was just that simple.

1. Go to Settings and tap on Wi-Fi.
2. Turn on the Wi-Fi and connect to a network.
3. Long press on the connected network and select Modify Network.
4. Check Show Advance Options.
5. On IP Settings drop down menu, select Static.
6. Assign IP of your choice but leave other variable untouched.

This may not be a total fix for businesses and educational establishments, because an IP address with need to be assigned. But for personal devices, this is a life saver!

For further information on this see, visit the article How to Fix Failed to Obtaining IP Address Error in Android.

How to stop MAC address from changing after, macchanger when first installed gives you the option of automatically changing MAC address with every new connection. since I don’t see the option on the —help page I would suggest uninstall and reinstall. The Yes/No option will crop up asking if you want it to randomize etc etc. Just select ‘No’, you should have …

How to stop MAC address from changing after disconnecting?

Network-Manager will reset your mac address during the wifi scanning.

To permanently change your mac address:

Edit your /etc/NetworkManager/NetworkManager.conf as follows:

[main] plugins=ifupdown,keyfile [ifupdown] managed=false [device] wifi.scan-rand-mac-address=no Wifi mac address is changing 

Edit your /etc/network/interfaces by adding the following line:

pre-up ifconfig wlp68s0b1 hw ether xx:xx:xx:yy:yy:yy 

The xx:xx:xx:yy:yy:yy is the new mac address obtained from the output of macchanger -A wlp68s0b1 .

Reboot and verify your settings.

Arch-linux wiki : Configuring MAC Address Randomization

Randomization during Wi-Fi scanning is enabled by default, but it may be disabled by adding the following lines to /etc/NetworkManager/NetworkManager.conf or a dedicated configuration file under /etc/NetworkManager/conf.d .

[device] wifi.scan-rand-mac-address=no 

Setting it to yes results in a randomly generated MAC address being used when probing for wireless networks.

If other methods cannot solve the problem, you can try to edit /etc/NetworkManager/conf.d/30-randomize-mac-address.conf

[connection-mac-randomization] ethernet.cloned-mac-address=permanent wifi.cloned-mac-address=permanent 

and keep wifi.scan-rand-mac-address=no .

• permanent: use the hardware MAC
• preserve: don’t change the MAC address of the device upon activation.
• random: generate a randomized value upon each connect.
• stable: generate a stable, hashed MAC address.

macchanger when first installed gives you the option of automatically changing MAC address with every new connection. since I don’t see the option on the —help page I would suggest uninstall and reinstall. The Yes/No option will crop up asking if you want it to randomize etc etc. Just select ‘No’, you should have smooth sailing from there.

Windows Hyper-V server has a default limit of 256, Hyper-V generates the MAC address as described below (mapping MAC address to aa-bb-cc-dd-ee-ff): The first three octets (aa-bb-cc) are Microsoft’s IEEE organizationally Unique Identifier, 00:15:5D (which is common on all Hyper-V hosts. The next two octets (dd-ee) are derived from the last two octets of the …

Does the source MAC address of a frame change when it passes through several switches? [duplicate]

No. If all the switches are layer-2 switches, the frames are switched without any changes.

Only with routers, including layer-3 switches where the packets need to cross to other VLANs, will the frames be stripped and rewritten for the new network or VLAN.

The MAC address is a unique identifier which is used by hosts on the local network.

If the switch were to change the destination MAC, the frame would not get delivered to the appropriate host. In the cases that it would, for example if the frame gets flooded, the destination host would drop it because it would no longer be destined for the host.

If the switch were to change the source MAC address, the destination host would use this MAC address for any responses (including updating any ARP entries with bad data). This would result in the same situation I already described, just for all return traffic.

Could mechanisms be developed to do this? I am sure they could. But there is no reason to do so at this point and this would only complicate networking and add unnecessary processing. We are not close to exhausting the available MAC address pool so there is no need for something like MAT (don’t know if the concept of MAC address translation even exists anywhere so maybe I just coined a term?).

Answered by @YLearn Why don’t switches rewrite mac-addresses?

How is the Uniqueness of MAC Addresses Enforced?, MAC spoofing is a technique for changing a factory-assigned Media Access Control (MAC) Address of a network interface on a networked device. The MAC Address is hard-coded on a network interface controller (NIC) and cannot be changed. However, there are tools which can make an operating system believe …

Same MAC on different interfaces

When a switch receives a frame from an interface, it creates an entry in the mac-address table with the source mac and interface. If the source mac is known, it will update the table with the new interface.

Is it possible that there is one MAC address associated to more interfaces in the switch MAC table?

No. A MAC address is an address of a unique NIC on the network, and each MAC address will only appear once in a switch’s MAC address table. If a there are more than one NICs on the same LAN that share the same MAC address, it will cause all sorts of communication issues.

If not, what is the behavior when frame with known MAC comes from a different interface?

The Switch will not store the same MAC address on multiple ports. It will simply update its MAC address table with the location of the most recent frame arriving with the duplicate MAC address. If both hosts are transmitting constantly, that will cause the MAC address entry to bounce between the two switch ports (known as MAC flapping ).

On the receiving side, the hosts will never get all the frames that are intended for them. Its like being in one conversation but only receiving every other word (and someone else receiving the remaining words).

Duplicate MAC addresses on the same L2 network causes both hosts to have communication issues. However, duplicate MAC addresses on different L2 networks (aka, separated by a router) will work just fine.

Yes it is possible via MAC spoofing. If you are seeing the same MAC address on multiple ports then it is possible that someone is in your network doing some not nice things.

Macos — I change the capitalization of a directory and Git, How to git mv on Mac Case-Sensitively. This is happening because Mac OS X implements case preserving and case insensitivity features that are intended to help you. Although the double rename suggestions in the other answer will work, I recommend the use of ‘—force’ for a best practice result: $ git mv —force …

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