Subj : Re: How do I get my Pi4 (Fedora) to use a real and stable MAC address?
To   : The Natural Philosopher
From : Lars Poulsen
Date : Tue Sep 17 2024 19:24:31

On 9/17/2024 2:44 AM, The Natural Philosopher wrote:
> On 16/09/2024 23:30, Lars Poulsen wrote:
>> On 9/15/2024 9:36 PM, The Natural Philosopher wrote:
>>> Unfortunately you are probably the only one here that is using RedHat
>>> on a Pi.
>>
>> You may well be right about that.
>>
>>> AFAIK, ethernet defaults to 'one permanent MAC address' - its only
>>> wifi that tends to switch around for security in public wifi spaces.
>>>
>>> Have you actually checked to see if you are getting ethernet
>>> randomisation?
>>> ifconfig -a will display it
>>
>> Thank you for an actually useful suggestion. I had forgotten to check
>> that and just assumed that was the cause of a change in IP address.
>>
>>
>>
> Hang on a minute.... IP address or MAC address?
>
> IP address may change any time you connect to the DHCP server (if you
> are using DHCP).
>
> ifconfig -a
> eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
>         *inet 192.168.0.101*  netmask 255.255.255.0  broadcast
> 192.168.0.255
>          inet6 fe80::9a2:3187:4600:cfc1  prefixlen 64  scopeid 0x20<link>
>         *ether d8:3a:dd:85:22:b1*  txqueuelen 1000  (Ethernet)
>          RX packets 335547  bytes 39007037 (37.2 MiB)
>          RX errors 0  dropped 158  overruns 0  frame 0
>          TX packets 348598  bytes 256465720 (244.5 MiB)
>          TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
>
> This is a statically configured *IP address* on a Pi 4B
> I assume the Ethernet *MAC* address is always the same.
>
> Looking up the MAC address online:
> Result:
> MAC Address Prefix    Manufacturer
> D83ADD                Raspberry Pi Trading Ltd

My DHCP server on that network has a list of known hosts (known by their
MAX address) and what their IP address should be. Hence my annoyance
when employees with iPhones have randomized MAC addresses.

The "hobby" RPI4 in my "work" network was acquired in the hope that it
may grow into being able  to become an edge router for my home network.

The edge router on my work network is a very nice headless AMD64 with 4
Gigabit ethernet ports running Fedora with iptables, OpenVPN and lots of
logging to keep the subnets behind it safe.

Considering the time I have spent on my RPI experiments, the savings on
the hardware have been a false economy.

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