Comment 4 for bug 291085

The network card is a Realtek 8168b according to the output below.

Assume it's an issue with the kernel driver (r8196), some general network support in the kernel, or less likely an issue with NetworkManager.

Note that this is the first time I've ever had to set an explicit MTU.

[ 2.612130] eth0: RTL8168b/8111b at 0xf88b2000, 00:18:f3:0e:cf:9d, XID 38000000 IRQ 221
[ 25.421075] r8169: eth0: link up
[ 25.421099] r8169: eth0: link up

02:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168B PCI Express Gigabit Ethernet controller (rev 01)
 Subsystem: ASUSTeK Computer Inc. Device 81aa
 Flags: bus master, fast devsel, latency 0, IRQ 221
 I/O ports at ee00 [size=256]
 Memory at fdbff000 (64-bit, non-prefetchable) [size=4K]
 [virtual] Expansion ROM at fdf00000 [disabled] [size=128K]
 Capabilities: [40] Power Management version 2
 Capabilities: [48] Vital Product Data <?>
 Capabilities: [50] Message Signalled Interrupts: Mask- 64bit+ Queue=0/1 Enable+
 Capabilities: [60] Express Endpoint, MSI 00
 Capabilities: [84] Vendor Specific Information <?>
 Capabilities: [100] Advanced Error Reporting <?>
 Capabilities: [12c] Virtual Channel <?>
 Capabilities: [148] Device Serial Number 68-81-ec-10-00-00-00-1a
 Capabilities: [154] Power Budgeting <?>
 Kernel driver in use: r8169
 Kernel modules: r8169

# uname -r
2.6.27-7-generic