On 2021-08-02 6:50 p.m., Cameron Simpson wrote:
On 02Aug2021 09:04, John Mellor <john.mellor@xxxxxxxxx> wrote:
On 2021-08-01 7:08 p.m., Cameron Simpson wrote:
We've got a few unmanaged netgear switches here and have had some
weirdness ourselves. I have lossely discovered that having my Mac on
both ethernet and wifi at once causes the LAN to go sour.
. . .
Huh? Am I misinterpreting? The MAC is supposed to be world-wide
unique to each interface.
As I said, the actual meachanism is unverified. We have strong
circumstantial evidence that if my Mac has wifi on and I activate the
ethernet as well, sometimes the local LAN wigs out. There's no router
stuff here - access to other hosts on the same LAN stops working.
Unmanaged switches involved, and power cycling a switch has sometimes
brought order again.
I conjecture stuff like ARP requests getting answered from the wrong
interface, or something. I'd have to experiment with tcpdump some time.
I don't have the same MAC on two interfeaces, but other confusion may
abound. I know the firewall complains constantly about this:
arp info overwritten for 172.16.3.17 by 00:f7:6f:d5:2d:d4 on vr2
arp info overwritten for 172.16.3.17 by 68:d9:3c:8a:bd:dd on vr2
I'm actually unsure what's using that address :-(
The only interfaces that I'm aware of that did that were the E1000 chips
that Intel made. They would once in a long while use the MAC in some
ARP packet from another machine as their own, breaking routing for the
whole network. There was no fix short of replacing all your Intel
ethernet cards and/or machines, as the error is in hardware.
If your Apple is using a USB-connected ethernet, maybe it has the
totally broken Intel chip?
--
John Mellor
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