On Fri, 14 Nov 2025 17:46:42 +0100 "Robin Jarry" <[email protected]> wrote:
> Morten Brørup, Nov 14, 2025 at 17:14: > >> From: Stephen Hemminger [mailto:[email protected]] > >> Reading the kernel source there is also special handling to include > >> device > >> id into link local address. This is to handle corner case where > >> multiple network > >> cards have same hardware MAC address. > > > > Multiple physical NICs should never have the same MAC address. > > Lots of stuff will break if they do. > > E.g. a network switch will forward packets to the NIC that most recently > > sent packets, so its MAC address was learned in the MAC address table in > > the switch. > > > > What is the use case justifying this tweak in the kernel? > > Some drivers expose multiple ports sharing the same mac address. > > This very is specific to certain hardware vendors. The comment here > refers to a change from 2005. I couldn't find the root commit/email. Yes, this code is in first git commit 2.6.12 from 2005 it is possible (but not worth the effort) to find it in earlier repos.
