Re: duplicate MAC - Re: 13.1R problems on Pi3

[It may be that you got your TO: and CC: list a
little mixed up. But I was listed as the TO:
and Bob P. as a CC: . I'm answering on that
basis but Bob P. is one with 2 RPi* that have
the same MAC address in use.]

On 2022-Jul-5, at 02:55, Ronald Klop <[email protected]> wrote:

> Van: Mark Millard <[email protected]>
> Datum: maandag, 4 juli 2022 20:47
> Aan: bob prohaska <[email protected]>
> CC: Karl Denninger <[email protected]>, [email protected]
> Onderwerp: Re: 13.1R problems on Pi3
> 
> On 2022-Jul-4, at 11:25, bob prohaska <[email protected]> wrote:
> 
> > On Mon, Jul 04, 2022 at 12:17:15PM -0400, Karl Denninger wrote:
> >>
> >> On 7/4/2022 11:28, bob prohaska wrote:
> >>> On Sun, Jul 03, 2022 at 10:36:35PM -0400, Karl Denninger wrote:
> >>>
> >>> Can any sense be made of the few ping responses obtained when ntp
> >>> is coming up? It's looks as if something happens after ntp runs
> >>> that blocks subsequent network traffic, but why starting an outbound
> >>> ping should partly unblock things is obscure to me.
> >>
> >> Yes.?? The odds are reasonably high that there is confusion as to which MAC
> >> address maps to which device.?? This implies there's a loop between the two
> >> switches (e.g. there is more than one way for packets to get into and out of
> >> each said switch to the other) or the two devices are claiming the same MAC
> >> address and thus when each "speaks" and performs ARP it "grabs" the map
> >> which works until the next one pipes up and it grabs it.
> >>
> >
> > Looks like that's the problem. There's only one cable between switches, but
> > here's what I get from ifconfig on each host:
> >
> > On the machine running 13.1-R attached to switch 2:
> > bob@www:~ % ifconfig
> > lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> metric 0 mtu 16384
> >   options=680003<RXCSUM,TXCSUM,LINKSTATE,RXCSUM_IPV6,TXCSUM_IPV6>
> >   inet6 ::1 prefixlen 128
> >   inet6 fe80::1%lo0 prefixlen 64 scopeid 0x1
> >   inet 127.0.0.1 netmask 0xff000000
> >   groups: lo
> >   nd6 options=21<PERFORMNUD,AUTO_LINKLOCAL>
> > ue0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
> >   options=80009<RXCSUM,VLAN_MTU,LINKSTATE>
> >>>>>>>>    ether b8:27:eb:71:46:4e
> >   inet 50.1.20.28 netmask 0xffffff00 broadcast 50.1.20.255
> >   media: Ethernet autoselect (100baseTX <full-duplex>)
> >   status: active
> >   nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
> > bob@www:~ % hostname
> > www.zefox.org
> > bob@www:~ %
> > bob@www:~ % uname -a
> > FreeBSD www.zefox.org 13.1-RELEASE FreeBSD 13.1-RELEASE releng/13.1-n250148-fc952ac2212 GENERIC arm64
> > bob@www:~ %
> >
> > On the machine running an updated stable/13 system attached to switch 1:
> > bob@pelorus:~ % ifconfig
> > lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> metric 0 mtu 16384
> >   options=680003<RXCSUM,TXCSUM,LINKSTATE,RXCSUM_IPV6,TXCSUM_IPV6>
> >   inet6 ::1 prefixlen 128
> >   inet6 fe80::1%lo0 prefixlen 64 scopeid 0x1
> >   inet 127.0.0.1 netmask 0xff000000
> >   groups: lo
> >   nd6 options=21<PERFORMNUD,AUTO_LINKLOCAL>
> > ue0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
> >   options=80009<RXCSUM,VLAN_MTU,LINKSTATE>
> >>>>>>>     ether b8:27:eb:71:46:4e
> >   inet 50.1.20.24 netmask 0xffffff00 broadcast 50.1.20.255
> >   media: Ethernet autoselect (100baseTX <full-duplex>)
> >   status: active
> >   nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
> > bob@pelorus:~ % hostname
> > pelorus.zefox.org
> > bob@pelorus:~ %
> > bob@pelorus:~ % uname -a
> > FreeBSD pelorus.zefox.org 13.1-STABLE FreeBSD 13.1-STABLE #6 stable/13-n251601-2353343b324: Sun Jul  3 21:43:04 PDT 2022     [email protected]:/usr/obj/usr/src/arm64.aarch64/sys/GENERIC arm64
> >
> >
> > Thinking it over, I added the extra switch some time ago and didn't
> > immediately notice any problems. Both Pi3s started out on the first
> > switch (NetGear), with no obvdious problems. Later I probably moved
> > one Pi3 to the second switch (D-Link) and started to notice troubles.
> > Does this story make sense?
> >
> >> Each interface device from the factory is supposed to have a unique MAC
> >> address.?? This can, for most interfaces, be overridden (modern Android
> >> phones "randomize" it if told to as a "security" measure) but for obvious
> >> reasons doing that can lead to problems. Collisions where multiple devices
> >> are using the same MAC will lead to exactly the sort of thing you're seeing
> >> because the switch is sending the packets to the wrong place.
> >>
> >> I've got a decent number of Pis of everything back to the "2" here and most
> >> of the time several of them are on my network at once.?? I've not seen this
> >> problem but I wouldn't exclude that both are claiming the same MAC and, if
> >> so, that's what's causing the problem.
> >>
> > [example ifconfig output snipped]
> >>
> >> That MUST be unique on your LAN; the prefix (first three octets) is a vendor
> >> code /*and the last three should never be duplicated by a vendor. */If you
> >> are not setting it in /etc/rc.conf or elsewhere and there /are /duplicates
> >> then a very bad thing happened when those units were manufactured -- set one
> >> of them to something else.
> >>
> >
> > Any pointers to MAC-setting methods appreciated.....
> 
> My example is not the best fit because it is for DHCP
> but in /etc/rc.conf I use (but showing "??"s):
> 
> ifconfig_dwc0="ether ??:??:??:??:??:?? DHCP"
> 
> to avoid its random assignment at power up.

FYI: The example system that has random assignment is
a Rock64, not a RPi* . I got the example line from the
Rock64's /etc/rc.conf file in order to show it to Bob
P.

I do not have such a line on any RPi* that I have
access to.

> So for you I would guess:
> 
> ifconfig_ue0="ether ??:??:??:??:??:?? inet 50.1.20.28 netmask 255.255.255.0"
> 
> 
> ===
> Mark Millard
> marklmi at yahoo.com
> 
>  
> 
> 
> Hi,
> 
> My Rpi3B+ does not have a random MAC on ue0.

Niether would the RPi3B that I have access to or any
of the other RPi* that I have access to.

> NB: It uses the muge driver:
> # devinfo | more
> ...
>       bcm283x_dwcotg0
>         usbus1
>           uhub0
>             uhub1
>               uhub2
>                 muge0
>                   miibus0
>                     ukphy0
> ...
> 
> Your current MAC is officially from the Raspberry Pi Foundation: https://hwaddress.com/oui-iab/B8-27-EB/ .

Not for a Rock64 --but true of the RPi* that I have access to.

> Could you have hardcoded the MAC in a *.dtb file or other config in the /boot directory and copied that over to the other RPI?

Bob P. is the one that reported 2 fixed MAC addresses on two
RPI3*'s that are equal (duplicates). I was trying to help
him make the machines not present a duplication.

> If you are going to assign some MAC yourself take a look at https://en.wikipedia.org/wiki/MAC_address#Universal_vs._local_(U/L_bit) to choose a locally administered MAC.

I expect that Bob P. will do something like that.


===
Mark Millard
marklmi at yahoo.com