4 ms·

> Legendarily it was HP (or was it sun?) who shipped a whole batch of ethernet cards accidentally in the 90s with the same MAC address, boy was that a nightmare

by quesera 13y ago

> Legendarily it was HP (or was it sun?) who shipped a whole batch of ethernet cards accidentally in the 90s with the same MAC address, boy was that a nightmare to figure out the hard way. Sun used to use the same MAC address on each port of their QFE (quad fast Ethernet) cards. It was easy to fix with ifconfig, but always made me wonder two things: a) if I number these ports sequentially (:a, :b, ...) am I going to collide with some other QFE card from the same batch, possibly from this same order of a dozen cards? And b) who thought this was a good idea? Was Sun just conserving MAC addresses on the theory that most QFE cards are 75% underutilized??

tedunangst 13y ago
That's because the MAC address is stored in system ROM on the motherboard, not in the NIC, iirc. The theory was 1) the ports would be used on different network segments, hence no problem and 2) storing the MAC in the motherboard meant you could swap NICs without updating all your DHCP/whatever config files.
- caf 13y ago
  On many SUN servers the MAC was stored on an externally-accessible smart card, which allowed you to swap out a broken machine and keep the same MAC.
- quesera 13y ago
  We might be comparing Sun hw from different eras. The QFE cards I remember were in a very different address range from the onboard Ethernet (which was still 8:0:20:... I think). Seems like the QFE MAC must have been in PRAM on the NIC then, at least. And I am pretty sure I remember the MAC address following the card, too. The problem I ran into was that when two same-MAC ports were connected to different segments/VLANs on the same layer 2 or 3 network device, that device wouldn't know what to do with the packets. Or it might send them down the wrong wire, which was a problem for me -- these were firewall boxes. :) Eventually Sun added a boot param (or a kernel config? Set from OBP or from a shell) that would automatically number the QFE interfaces sequentially on boot. That fixed the problem for me. Much later, they added the front-panel accessible smart cards that contained MAC, hostid, etc. I think that was the Netra series, intended for carrier grade RAIC installations.
- cnvogel 13y ago
  ...and, additionally, connecting several ports to the same network segment/switch in many cases gave you immediate, effortless load-balancing.

by quesera 13y ago

tedunangst 13y ago

That's because the MAC address is stored in system ROM on the motherboard, not in the NIC, iirc. The theory was 1) the ports would be used on different network segments, hence no problem and 2) storing the MAC in the motherboard meant you could swap NICs without updating all your DHCP/whatever config files.

caf 13y ago
On many SUN servers the MAC was stored on an externally-accessible smart card, which allowed you to swap out a broken machine and keep the same MAC.
quesera 13y ago
We might be comparing Sun hw from different eras. The QFE cards I remember were in a very different address range from the onboard Ethernet (which was still 8:0:20:... I think). Seems like the QFE MAC must have been in PRAM on the NIC then, at least. And I am pretty sure I remember the MAC address following the card, too. The problem I ran into was that when two same-MAC ports were connected to different segments/VLANs on the same layer 2 or 3 network device, that device wouldn't know what to do with the packets. Or it might send them down the wrong wire, which was a problem for me -- these were firewall boxes. :) Eventually Sun added a boot param (or a kernel config? Set from OBP or from a shell) that would automatically number the QFE interfaces sequentially on boot. That fixed the problem for me. Much later, they added the front-panel accessible smart cards that contained MAC, hostid, etc. I think that was the Netra series, intended for carrier grade RAIC installations.
cnvogel 13y ago
...and, additionally, connecting several ports to the same network segment/switch in many cases gave you immediate, effortless load-balancing.