Two Raspberry Pi 3s purchased about a year apart turned out to
have duplicate MAC addresses. Anybody else seen this?
A correspondent told me about a config.txt variable
force_mac_address which seems to have worked around
the problem. I incremented the last digit by one and
all seems well, but it was a real hair puller for six
months. Kept thinking it was an error on my part.
Thanks for reading,
bob prohaska
Two Raspberry Pi 3s purchased about a year apart turned out to
have duplicate MAC addresses. Anybody else seen this?
A correspondent told me about a config.txt variable
force_mac_address which seems to have worked around
the problem. I incremented the last digit by one and
all seems well, but it was a real hair puller for six
months. Kept thinking it was an error on my part.
Thanks for reading,
bob prohaska
On 2022-07-06, bob prohaska <bp@www.zefox.net> wrote:
Two Raspberry Pi 3s purchased about a year apart turned out to
have duplicate MAC addresses. Anybody else seen this?
I'm surprized. It's the sort of thing one expects with cheap copycat knockoffs.
Have you put anything on the rpi forum?
Two Raspberry Pi 3s purchased about a year apart turned out to
have duplicate MAC addresses. Anybody else seen this?
A correspondent told me about a config.txt variable
force_mac_address which seems to have worked around
the problem. I incremented the last digit by one and
all seems well, but it was a real hair puller for six
months. Kept thinking it was an error on my part.
Thanks for reading,
bob prohaska
Two Raspberry Pi 3s purchased about a year apart turned out to
have duplicate MAC addresses. Anybody else seen this?
A correspondent told me about a config.txt variable
force_mac_address which seems to have worked around
the problem. I incremented the last digit by one and
all seems well, but it was a real hair puller for six
months. Kept thinking it was an error on my part.
Please check if they really have the same MAC address when booted from
a new installed OS. It is possible to change the MAC address.
The MAC address of the physical interface (not any virtual interface)
should have an unique MAC address by default from the vendor.
You can override this if they really have the same MAC by default.
Are the MAC addresses in the Broadcom MAC address allocation - I
think it starts B8: ?
(a Pi 3 here has B8:27:EB)
I vaguely understood that pre-Pi4 there's no nonvolatile storage on
the board to hold the MAC address, so I believe it's generated programmatically in the boot process (from the serial number, I
presume). It would seem surprising to have a collision.
The Pi4 has a proper EEPROM holding the boot firmware so there's
scope to store the MAC in there - I haven't checked they do that
though.
Am Dienstag, 12. Januar 106, um 10:41:46 Uhr schrieb Theo:
Are the MAC addresses in the Broadcom MAC address allocation - I
think it starts B8: ?
(a Pi 3 here has B8:27:EB)
Normally they are assigned to the board manufacturer - regardless of
the Ethernet controller that is being used.
My Pi 3 also begins with b8:27:eb that is assigned to Raspberry Pi Foundation.
The chip is from Microchip Technology, Inc. (formerly SMSC).
Marco Moock <mo01@posteo.de> wrote:
Please check if they really have the same MAC address when booted from
a new installed OS. It is possible to change the MAC address.
The MAC address of the physical interface (not any virtual interface)
should have an unique MAC address by default from the vendor.
You can override this if they really have the same MAC by default.
Are the MAC addresses in the Broadcom MAC address allocation - I think it starts B8: ?
(a Pi 3 here has B8:27:EB)
I vaguely understood that pre-Pi4 there's no nonvolatile storage on the
board to hold the MAC address, so I believe it's generated
programmatically
in the boot process (from the serial number, I presume). It would seem surprising to have a collision.
The Pi4 has a proper EEPROM holding the boot firmware so there's scope to store the MAC in there - I haven't checked they do that though.
"Theo" <theom+news@chiark.greenend.org.uk> wrote in message news:2YA*wt6Sy@news.chiark.greenend.org.uk...
Marco Moock <mo01@posteo.de> wrote:
Please check if they really have the same MAC address when booted from
a new installed OS. It is possible to change the MAC address.
The MAC address of the physical interface (not any virtual interface)
should have an unique MAC address by default from the vendor.
You can override this if they really have the same MAC by default.
Are the MAC addresses in the Broadcom MAC address allocation - I think it
starts B8: ?
(a Pi 3 here has B8:27:EB)
I vaguely understood that pre-Pi4 there's no nonvolatile storage on the
board to hold the MAC address, so I believe it's generated
programmatically
in the boot process (from the serial number, I presume). It would seem
surprising to have a collision.
The Pi4 has a proper EEPROM holding the boot firmware so there's scope to
store the MAC in there - I haven't checked they do that though.
Where do network adapters (PCI card or onboard) normally hold their MAC address.
I've never heard of two devices happening to have the same MAC
address so I assumed that part of the manufacturing process was to
allocate a unique, never-to-be-allocated-again address from a pool that
the vendor had "bought". Sounds like a problem if RasPi have allocated duplicate MAC addresses. It would make sense for the Pi build process to allocate a serial number and a MAC address which were related, so the Pi
3 calculates it and the Pi 4 reads it from non-vol memory that is set at build time.
What are the implications of duplicate MAC? Is it only a problem within
a LAN, or can it be a problem when two devices are on different private
LANs (192.168.x.x IP addresses) and the only communication is by
different WAN addresses? Is it worse for IPv6 which has no NAT (network address translation) stage?
The Pi4 has a proper EEPROM holding the boot firmware so there's scope to store the MAC in there - I haven't checked they do that though.
Normally there is some kind of prom on board. The software reads it but
does not have to use it.
What are the implications of duplicate MAC? Is it only a problem
within a LAN, or can it be a problem when two devices are on
different private LANs (192.168.x.x IP addresses) and the only
communication is by different WAN addresses? Is it worse for IPv6
which has no NAT (network address translation) stage?
On Thu, 14 Jul 2022 10:03:59 +0100, The Natural Philosopher wrote:
Yes. I've always set IPs for computers on my LAN by putting its IP in "/etc/hosts" (note that the first two lines wrap):
Normally there is some kind of prom on board. The software reads it but
does not have to use it.
$ cat /etc/hosts
127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4
::1 localhost localhost.localdomain localhost6 localhost6.localdomain6
192.168.7.5 rpi.gregorie.lan rpi
and I run a local copy of 'named' on my house server, which resolves the names of all computers on my local LAN and passes all other address to external name servers for resolution. This works well, with my Pi2 using
the IP I configured it to use.
Am Donnerstag, 14. Juli 2022, um 09:35:08 Uhr schrieb NY:
What are the implications of duplicate MAC? Is it only a problem
within a LAN, or can it be a problem when two devices are on
different private LANs (192.168.x.x IP addresses) and the only
communication is by different WAN addresses? Is it worse for IPv6
which has no NAT (network address translation) stage?
MAC addresses come from Ethernet and are not related to IP addresses.
On an ethernet link (the network with patch cables, Repeaters, Hubs and Switched or even Buses for 10 Base2/5) a MAC address must be unique.
A router separates two ethernet links. NAT is relevant here. IPv4/IPv6
also not.
They just have a problem too because packages will not reach their
intended destination in a switched network if duplicated MACs exist.
A router just forwards the IP packet. If the other link is also based
on ethernet new MAC source and targets will be padded to the IP packet
and are a new frame on a separate link.
I'm intrigued: why would you choose to set the IP address statically at the >computer (equivalent of doing so with a Windows PC) rather than keeping the >default DHCP configuration and letting the address-reservation feature of >almost all modern routers take care of the fixed MAC-IP mapping for those >devices which need fixed IP addresses?
So *in theory* everybody could use the same set of MAC addresses, as long
as no two computers *on the same LAN* shared a MAC address?
I suppose the fact that all network adaptors (apart from Raspberry Pis!)
have unique MAC addresses is mainly to avoid MAC address clashes for two computers on the same LAN.
"Martin Gregorie" <martin@mydomain.invalid> wrote in message news:taoui3$2moa7$1@dont-email.me...
On Thu, 14 Jul 2022 10:03:59 +0100, The Natural Philosopher wrote:
Yes. I've always set IPs for computers on my LAN by putting its IP in
Normally there is some kind of prom on board. The software reads it but
does not have to use it.
"/etc/hosts" (note that the first two lines wrap):
$ cat /etc/hosts
127.0.0.1 localhost localhost.localdomain localhost4
localhost4.localdomain4
::1 localhost localhost.localdomain localhost6
localhost6.localdomain6
192.168.7.5 rpi.gregorie.lan rpi
and I run a local copy of 'named' on my house server, which resolves the
names of all computers on my local LAN and passes all other address to
external name servers for resolution. This works well, with my Pi2 using
the IP I configured it to use.
I'm intrigued: why would you choose to set the IP address statically at
the computer (equivalent of doing so with a Windows PC) rather than
keeping the default DHCP configuration and letting the
address-reservation feature of almost all modern routers take care of
the fixed MAC-IP mapping for those devices which need fixed IP addresses?
variable IP addresses is as practical as having everybodies phone number change every day. All computahs on my LAN have fixed IP addresses,
So the network still works with the router switched off?
On a sunny day (Thu, 14 Jul 2022 13:46:29 +0100) it happened "NY" <me@privacy.invalid> wrote in <tap3gl$2ndru$1@dont-email.me>:
I'm intrigued: why would you choose to set the IP address statically at
the
computer (equivalent of doing so with a Windows PC) rather than keeping
the
default DHCP configuration and letting the address-reservation feature of >>almost all modern routers take care of the fixed MAC-IP mapping for those >>devices which need fixed IP addresses?
variable IP addresses is as practical as having everybodies phone number change every day.
All computahs on my LAN have fixed IP addresses,
very useful if you use scp, netcat, ssh, scripts, etc.
You can also set names for each IP address in /etc/host
"The Natural Philosopher" <tnp@invalid.invalid> wrote in message news:tapb5q$2o694$1@dont-email.me...
So the network still works with the router switched off?
Fair enough. I suppose it allows you to reboot the router or move it
from one place / mains socket to another. But only if the LAN segments
to all the computers are connected via a separate network switch, and
none are connected by wireless using the router's wifi.
On Thu, 14 Jul 2022 13:44:25 GMT
Jan Panteltje <pNaonStpealmtje@yahoo.com> wrote:
variable IP addresses is as practical as having everybodies phone number
change every day. All computahs on my LAN have fixed IP addresses,
I used to do that, and some things like the jailed services still do
have fixed IP addresses but most machines (computers, phones, TVs ...) get >dynamic addresses and if I'm likely to want to connect to them set a host >name which gets picked up by the DHCP server and added to the local DNS so
I never need to care what IP gets used.
So *in theory* everybody could use the same set of MAC addresses, as
long as no two computers *on the same LAN* shared a MAC address?
I suppose the fact that all network adaptors (apart from Raspberry
Pis!) have unique MAC addresses is mainly to avoid MAC address
clashes for two computers on the same LAN.
If I want to go online with my smartphone it has separate prepayed 4G
card. When elsewhere I can take the 4G Huawei USB modem stick that now
sits in a Pi4 at IP address 192.168.178.1 configured as router and put it
in my laptop, internet everywhere, Definitely not a 'normal system'.. But
I have full control. If something ever needs WiFi then I can always start dhcpcd on some raspi.
Am Dienstag, 12. Januar 106, um 10:41:46 Uhr schrieb Theo:
Are the MAC addresses in the Broadcom MAC address allocation - I
think it starts B8: ?
(a Pi 3 here has B8:27:EB)
Normally they are assigned to the board manufacturer - regardless of
the Ethernet controller that is being used.
My Pi 3 also begins with b8:27:eb that is assigned to Raspberry Pi Foundation.
The chip is from Microchip Technology, Inc. (formerly SMSC).
"The Natural Philosopher" <tnp@invalid.invalid> wrote in message news:tapb5q$2o694$1@dont-email.me...Do any serious computer people still use wifi?
So the network still works with the router switched off?
Fair enough. I suppose it allows you to reboot the router or move it
from one place / mains socket to another. But only if the LAN segments
to all the computers are connected via a separate network switch, and
none are connected by wireless using the router's wifi.
Do any serious computer people still use wifi?
On 13/07/2022 11:32, Marco Moock wrote:
The chip is from Microchip Technology, Inc. (formerly SMSC).
I've got several different types reported by my Pis
MAC Address: DC:A6:32:XX:XX:XX (Raspberry Pi Trading)
MAC Address: 08:6A:0A:XX:XX:XX (Askey Computer)
MAC Address: E4:5F:01:XX:XX:XX (Unknown)
MAC Address: B8:27:EB:XX:XX:XX (Raspberry Pi Foundation)
On 14/07/2022 16:39, NY wrote:
"The Natural Philosopher" <tnp@invalid.invalid> wrote in messageDo any serious computer people still use wifi?
news:tapb5q$2o694$1@dont-email.me...
So the network still works with the router switched off?
Fair enough. I suppose it allows you to reboot the router or move it from
one place / mains socket to another. But only if the LAN segments to all
the computers are connected via a separate network switch, and none are
connected by wireless using the router's wifi.
schrieb druck:
Marco Moock wrote:
The chip is from Microchip Technology, Inc. (formerly SMSC).
I've got several different types reported by my Pis
MAC Address: DC:A6:32:XX:XX:XX (Raspberry Pi Trading)
MAC Address: 08:6A:0A:XX:XX:XX (Askey Computer)
MAC Address: E4:5F:01:XX:XX:XX (Unknown)
MAC Address: B8:27:EB:XX:XX:XX (Raspberry Pi Foundation)
The MAC addresses are assigned to the Board - regardless of which
ethernet controller is being used. I have an ASUS motherbaord with a
Realtek chip, the MAC is assigned to ASUS.
Some vendors like Intel have more than one manufacturer code. It seems
that Raspi also has that.
My company deploys Cisco routers. Each Cisco router uses only one MAC
for all of its ethernet ports.
What are the implications of duplicate MAC? Is it only a problem within
a LAN, or can it be a problem when two devices are on different private
LANs (192.168.x.x IP addresses) and the only communication is by
different WAN addresses?
Den 2022-07-14 kl. 10:35, skrev NY:
What are the implications of duplicate MAC? Is it only a problem
within a LAN, or can it be a problem when two devices are on different
private LANs (192.168.x.x IP addresses) and the only communication is
by different WAN addresses?
Easy to test with virtual machines.
You get a random MAC from the setup - but you may set it to what you'd
like.
I think ARP only works withn the same subnet.
Or at least ARP is non-routable.
So same MAC on devices on networks that need routing between them are ok.
On same network - bad idea
I think ARP only works withn the same subnet.
Or at least ARP is non-routable.
So same MAC on devices on networks that need routing between them are
ok.
On same network - bad idea
ARP is an Ethernet protocol like IPv4 and IPv6.
On Sat, 16 Jul 2022 16:34:08 +0200
Marco Moock <mo01@posteo.de> wrote:
ARP is an Ethernet protocol like IPv4 and IPv6.
This is wrong! (everything else you said was right though).
ARP is a protocol specifically for IP over ethernet, it
provides the mapping between ethernet addresses (MAC) and IP
addresses.
IPv4 and IPv6 are however *not* ethernet protocols. They can
be (and often are) carried over ethernet but they can also be carried
over serial lines with SLIP or PPP, token ring networks, carrier
pigeons, DNS updates and *any* other packet or stream based
communication channel.
Additionally, ARP is only for mapping IPv4 addresses to MAC addresses.
Indeed: my gateway router/firewall is separate from my LAN hub, which is
just a switch.
schrieb Don:
My company deploys Cisco routers. Each Cisco router uses only one MAC
for all of its ethernet ports.
Is that really the case?
What about the virtual VLAN ports?
These can be interconnected with each other. Doesn't that create
problems when they all have the same MAC address?
Martin Gregorie <martin@mydomain.invalid> wrote:
Indeed: my gateway router/firewall is separate from my LAN hub,
which is just a switch.
Hubs and switches are different things. A hub is dumb, connects
everything to everything. A switch knows about network addresses. So
it's "just a hub" or "a switch".
It is getting more difficult to find true hubs, though, because of featuritis.
It will be difficult doing that mapping if there is a one-to-many
relation between IP-addresses and MACs
On Sat, 16 Jul 2022 16:34:08 +0200
Marco Moock <mo01@posteo.de> wrote:
ARP is an Ethernet protocol like IPv4 and IPv6.
This is wrong! (everything else you said was right though).
ARP is a protocol specifically for IP over ethernet, it provides the mapping between ethernet addresses (MAC) and IP addresses.
IPv4 and IPv6 are however *not* ethernet protocols. They can be (and often are) carried over ethernet but they can also be carried over serial lines with SLIP or PPP, token ring networks, carrier pigeons, DNS updates
and *any* other packet or stream based communication channel.
On Sat, 16 Jul 2022 20:47:23 +0200, Marco Moock wrote:
Additionally, ARP is only for mapping IPv4 addresses to MAC addresses.
Which is why I brought i up.
Someone (OP?) wanted to know impact on network with duplicate MACs
It will be difficult doing that mapping if there is a one-to-many relation between IP-addresses and MACs
Yes. Or rather the other way round - a one to many relation between
mac addresses and IP addresses....
It is not just for Ethernet. It also works on e.g. WiFi and Decnet to
name but two
Am Samstag, 16. Juli 2022, um 23:56:16 Uhr schrieb The Natural
Philosopher:
It is not just for Ethernet. It also works on e.g. WiFi and Decnet to
name but two
Is the ARP protocol for Ethernet different from ARP for WiFi?
They both use MAC addresses, the only difference I know is that WiFi
supports a hight MTU than Ethernet.
Am Samstag, 16. Juli 2022, um 23:56:16 Uhr schrieb The Natural
Philosopher:
It is not just for Ethernet. It also works on e.g. WiFi and Decnet to
name but two
Is the ARP protocol for Ethernet different from ARP for WiFi?
They both use MAC addresses, the only difference I know is that WiFi
supports a hight MTU than Ethernet.
On 17.7.22 11.42, Marco Moock wrote:
Am Samstag, 16. Juli 2022, um 23:56:16 Uhr schrieb The Natural
Philosopher:
It is not just for Ethernet. It also works on e.g. WiFi and Decnet to
name but two
Is the ARP protocol for Ethernet different from ARP for WiFi?
They both use MAC addresses, the only difference I know is that WiFi
supports a hight MTU than Ethernet.
ARP is a protocol for resolving IPv4 addresses from hardware
addresses in a broadcast-capable local net. IPv6 has its
own neighbor discovery protocol.
Beside Ethernet, the current IANA hardware type catalog
lists 39 other hardware types, including e.g. Token Ring,
ARCNET, ATM and SDLC/HDLC.
Beside Ethernet, the current IANA hardware type catalog
lists 39 other hardware types, including e.g. Token Ring,
ARCNET, ATM and SDLC/HDLC.
Am Sonntag, 17. Juli 2022, um 19:27:42 Uhr schrieb Tauno Voipio:
Beside Ethernet, the current IANA hardware type catalog
lists 39 other hardware types, including e.g. Token Ring,
ARCNET, ATM and SDLC/HDLC.
Could you please give a link?
It would interest me.
I only know Ethernet with its many standard like 10BaseT, 10Base2 etc. ARCNET, TokenRing/TokenBu and WiFi.
My company deploys Cisco routers. Each Cisco router uses only one MAC
for all of its ethernet ports.
Is that really the case?
>> My company deploys Cisco routers. Each Cisco router uses only one MAC
>> for all of its ethernet ports.
MM> Is that really the case?
Not on the Cisco's I use daily - each port has a unique MAC.
cisco L3 switch, rather than cisco router?
Not on the Cisco's I use daily - each port has a unique MAC.
cisco L3 switch, rather than cisco router?
schrieb Andy Burns:
cisco L3 switch, rather than cisco router?
Despite the name - they do the same activities.
Current cisco routers
don't even allow routing based on physical ports.
They also provide
switching capabilities on all their ports.
Marco Moock wrote:
schrieb Andy Burns:
cisco L3 switch, rather than cisco router?
Despite the name - they do the same activities.
agreed, but they sell devices they call switches, and they sell other devices they call routers.
*** typos in original followup corrected ***
Andy Burns wrote:
Marco Moock wrote:
schrieb Andy Burns:
cisco L3 switch, rather than cisco router?
Despite the name - they do the same activities.
agreed, but they sell devices they call switches, and they sell
other devices they call routers.
My company deploys humble Cisco hardware. (Thank God almighty!) And,
in my circumstance, the devices Cisco calls routers do different
activities than the devices they call switches.
For instance, let's take a peek at the unique ip configuration subcommands for my humble routers:
even if you do a "no switchport" on the interface?
My company deploys humble Cisco hardware. (Thank God almighty!) And,
| Sysop: | deepend |
|---|---|
| Location: | Calgary, Alberta |
| Users: | 240 |
| Nodes: | 10 (0 / 10) |
| Uptime: | 17:16:24 |
| Calls: | 1,464 |
| Files: | 3,372 |
| Messages: | 360,551 |