There seems to be an Ethernet issue with Apple?s latest Intel based laptop, the MacBook Pro. My machine experiences terrible packet loss when connected to some Ethernet LANs seemingly without any rhyme or reason. I would typically see about 60% to 70% packet loss when pinging another host on the local network. Plugging my older PowerBook into the same network and pinging that same host resulted in 0% packet loss and plugging the two Macs directly into eachother without a hub or a switch in the middle worked perfectly as well. So I tried an assortment of hubs and switches guessing that there was a problem on the electronic signaling layer. Still no luck! So I called Apple and ran through their battery of tests. Eventually I ended up mailing the machine back to them for repair. A few days later, the machine showed up again with a little piece of paper saying that they couldn?t find anything wrong with it! Dang it! There is something wrong with this thing! Why didn?t they call me first before sending it back? So I decided to so a little digging on my own instead and have come up with some interesting results.

As it turns out, all of the LANs I use employ 802.1Q VLAN tagging. I suppose this is because I?m heavily into VoIP these days and separation of VoIP and Data networks is usually done with 802.1Q VLANs. This is true on all the LANs I use at work and home, but of course isn?t true when I forgo the LAN and connect directly from machine to machine. I have been able to demonstrate this quite effectively by connecting my MacBook to a switch without VLAN tagging. After plugging another host into that network, I can happily ping back and forth all day long with 0% packet loss. However, when I plug the uplink into my Cisco switch, which uses VLANs, pings are immediately sporadic and packet loss goes sky high.

This is, presumably, a software issue though it doesn?t really make sense that an X86 compiler instead of a PowerPC compiler would create such a bug. About the only thing I can come up with is that this is either some very unlikely hardware bug, or the two machines use differient Ethernet hardware and there is a problem in the new Ethernet driver.

I decided to do a little detective work and find out exactly what manufacturer makes the Ethernet hardware in the MacBook Pro. A search on the first part of my MAC address comes up with Apple Computer. That?s not very helpful because a search on the MAC address of my old PowerBook comes up with the same thing. (Apple has 13 MAC address ranges as of the writing of this story.) It looks like I?d have to crack my MacBook Pro open to find out who makes the Ethernet. I?d say there?s a very strong chance that it is a different manufacturer than the Ethernet in the PowerBook, so maybe the driver idea isn?t far off. So much for my detective work.

So what?s a good workaround if you have VLAN traffic on your LAN? Well, you could wall yourself off somehow by camping out on a LAN behind a NAT device. An AirPort would work well for this as would an old Linksys ?router?. I?m probably going to ?borrow? a VLAN aware switch and hard-set the port to non-VLAN and see if that works. In the meantime, I hope Apple announces a software update that fixes this or I?m going to have to give this thing back. Ethernet is probably the most important thing I plug into the side of my Mac. Without that, I?m going back to my PowerBook.