Duplicate MAC addresses

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.

Indeed: my gateway router/firewall is separate from my LAN hub, which is just a switch.

On a sunny day (Thu, 14 Jul 2022 16:15:29 +0100) it happened Ahem A Rivet's Shot snipped-for-privacy@eircom.net wrote in snipped-for-privacy@eircom.net:

I have a lot of Microchip PIC stuff I designed on the LAN, IP address and MAC is programmed in EEPROM in those chips, for example the LED light controller. WiFi is off here, all is wired, because wifi security is totally broken.

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 Donnerstag, 14. Juli 2022, um 13:51:14 Uhr schrieb NY:

Replace LAN with ethernet link and it is true. LAN isn't that specific, a local area network CAN be splitted up by routers (common in bigger business networks).

True, is should be possible to put them all together in one ethernet link.

In 2006 I bought 2 industrial PCs with 3 LAN ports and built firewall (the one is intended as backup of the other). It still works great 16y later I put the WLAN modem infront of the firewall and the PCs are behind.

I find this setup the most simple one.

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)

---druck

Do any serious computer people still use wifi?

Most of the house is wired with CAT-6 and most things are plugged in but I fitted a couple of Unifi ceiling mount APs a few years back, there are a number of things in the house that use them - phones, laptops, a TV that gets moved around, visitors ... it works fine. But then I live out in the country where the neighbours are far enough away that there's no interference and someone wardriving would be very conspicuous.

Am Freitag, 15. Juli 2022, um 00:03:15 Uhr schrieb druck:

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.

I use Ethernet for my computers, including my PVR computer etc, and the TV. Everything which it is easy to cable to the router. And things which need a reliable connection - my experience with wifi is that it can sometimes go loopy (lost connection or unusually slow) which requires a device to be rebooted, which is not possible when you are trying to access a computer remotely over Teamviewer or Real VNC while away from home.

I also have a Linksys Velop mesh network which provides wifi to the rest of the house, for portable devices like laptops, phones, tablets which mainly need to access the internet but which don't generate heavy traffic within the house. Having said that, my laptop can quite happily access my PVR over wifi, for editing out continuity/commercials for programmes that I want to keep. It's a bit slower than Ethernet: it seems to average about 30-70 MB/sec (so about 300 - 700 Mb/sec) rather than about 80 MB/sec over Ethernet, but that's only an issue for local traffic, because internet WAN traffic is limited to around 30 for my FTTC connection.

Both Ethernet and wifi have their place. It's a damn sight easier to use wifi than to have to run Cat7 cable up into the loft, and then down into other rooms, just for wifi-only devices like phones and tablets. One of the mesh nodes also feeds Ethernet to the Hive hub which needs to be within wireless (proprietary, not wifi) range of the thermostats and the central heating controller, so can't be placed near the router (I tried...).

The problem with the Velop system is that you can't control which nodes do or don't have 2.4 GHz enabled - its all or none. I have a few older devices that only talk 2.4 and not 5 GHz, so I need 2.4 turned on, but that means that the five nodes have overlapping 2.4 coverage if they are placed just at the limiting distance for 5 GHz backhaul to the primary node. This means that if there is a power cut and the nodes all turn on simultaneously, they spend a long time faffing around while they try to work out which 2.4 channels they can use to minimise overlaps. I did have 6 nodes but I found out by trial and error than if one of them was turned off, I still got good coverage and it took less time for nodes to negotiate channels.

Allow me to add a few details.

My company deploys Cisco routers. Each Cisco router uses only one MAC for all of its ethernet ports.

The first three groups of two hexadecimal digits in a MAC typically designate a manufacturer's organizationally unique identifier (OUI):

According to Edward Snowden, the US National Security Agency has a system that tracks the movements of mobile devices in a city by monitoring MAC addresses.[20] To avert this practice, Apple has started using random MAC addresses in iOS devices while scanning for networks. Other vendors followed quickly. MAC address randomization during scanning was added in Android starting from version 6.0, Windows 10, and Linux kernel 3.18.

Am Freitag, 15. Juli 2022, um 18:47:29 Uhr schrieb Don:

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?

Den 2022-07-14 kl. 10:35, skrev NY:

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

ARP is an ethernet protocol really as much as an IP protocol.

Yup.

Am Samstag, 16. Juli 2022, um 11:52:40 Uhr schrieb Björn Lundin:

ARP is an Ethernet protocol like IPv4 and IPv6. Only IPv4 and IPv6 will be forwarded (routed) to another Ethernet link by a router. ARP isn't IPv6 nor IPv4, so won't be forwarded. It will stay inside the Ethernet link is was sent on, sometimes referred as broadcast domain because ARP is being sent to FF:FF:FF:FF:FF:FF (Ethernet broadcast address). ARP only makes sense if the recipient is on the same Ethernet link.

Not completely right. It is possible to have more than one subnet on one Ethernet link. For IPv6 this is the default (fe80::/64 and

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.

Am Samstag, 16. Juli 2022, um 18:10:15 Uhr schrieb Ahem A Rivet's Shot:

ARP makes no sense without ethernet, there you are right, but what is the difference to other protocols? Both are just payload for Ethernet. I am aware that there are other physical layer protocols that can carry IPv4/IPv6. Additionally, ARP is only for mapping IPv4 addresses to MAC addresses. For IPv6 the Neighbor Discovery Protocol (NDP) exists that uses ICMPv6 inside of an IPv6 packet, so it is not a separate Protocol like ARP for IPv4.

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

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.