We recently swapped out our Cisco 2970 access switches with a 4500 series switch. No one on the network noticed anything except for a single user running Ubuntu (95% of our users are OS X users. The only other Ubuntu user in the office is not experiencing this issue either).
From the user's perspective, their ethernet network connection is simply not available, similar to it being plugged in to a shutdown switch port.
While the machine is booting, before Ubuntu finishes loading, the network card is active, and the switch sees an established link.
Once Ubuntu finishes booting, the network card no longer holds an establishes connection to the switch. Watching the interface stats on the switch I can see it going from an Up state to Down, sitting on Down for a couple of seconds, very briefly flicking back to Up and repeating.
On the Ubuntu side it says the network is disconnected.
We're found a weird work around, where by plugging this Ubuntu machine directly into a neighbour's MacBook pro, setting a static IP on each machine, ensuring ping between the two machines, then plugging the Ubuntu machine back into the switch and changing the static IP back to DHCP assigned. Once this is completed the Ubuntu machine holds a solid connection with the switch.
As soon as the user reboots their Ubuntu machine, this process must be repeated before the network connection is stable.
The user is running Ubuntu 14.10, a Realtek NIC and we're running Cisco 4500 IOS 15.0(2)SG8.
On the old 2970 switch this user (with the same Ubuntu setup) had no issues. That was running IOS 12.
Any thoughts?
