Q:

Ubuntu Network Error (Ubuntu 12.04)

We run a 1000BaseT, full duplex network, however we use auto-negotiate to ensure that minimal errors occur. A few days ago, all Ubuntu servers started having an extremely slow upload (to the outside world) speed, whilst maintaining the usual download speed. For example, we may usually have 100 down and 100 up, however we would now be receiving 100 down and 1 up.
This only applies to Ubuntu machines, as all Windows machines (both the server and my admin laptop) receive the full speed. 
All Ubuntu machines are currently using the 3.13.0-48-generic kernel(and I have tried downgrading the kernel, however it fixed nothing). 
Below is some information I have gathered from various debug tools:
ethtool:
Supported ports: [ TP ]
Supported link modes:   10baseT/Half 10baseT/Full
                        100baseT/Half 100baseT/Full
                        1000baseT/Full
Supported pause frame use: No
Supports auto-negotiation: Yes
Advertised link modes:  10baseT/Half 10baseT/Full
                        100baseT/Half 100baseT/Full
                        1000baseT/Full
Advertised pause frame use: No
Advertised auto-negotiation: Yes
Speed: 1000Mb/s
Duplex: Full
Port: Twisted Pair
PHYAD: 1
Transceiver: internal
Auto-negotiation: on
MDI-X: Unknown
Supports Wake-on: g
Wake-on: d
Link detected: yes 

mii-tool:
eth0: negotiated 1000baseT-FD flow-control, link ok

lspci:
00:00.0 Host bridge: Intel Corporation 5000X Chipset Memory Controller Hub (rev 12)
00:02.0 PCI bridge: Intel Corporation 5000 Series Chipset PCI Express x4 Port 2 (rev 12)
00:03.0 PCI bridge: Intel Corporation 5000 Series Chipset PCI Express x4 Port 3 (rev 12)
00:04.0 PCI bridge: Intel Corporation 5000 Series Chipset PCI Express x8 Port 4-5 (rev 12)
00:05.0 PCI bridge: Intel Corporation 5000 Series Chipset PCI Express x4 Port 5 (rev 12)
00:06.0 PCI bridge: Intel Corporation 5000 Series Chipset PCI Express x8 Port 6-7 (rev 12)
00:07.0 PCI bridge: Intel Corporation 5000 Series Chipset PCI Express x4 Port 7 (rev 12)
00:10.0 Host bridge: Intel Corporation 5000 Series Chipset FSB Registers (rev 12)
00:10.1 Host bridge: Intel Corporation 5000 Series Chipset FSB Registers (rev 12)
00:10.2 Host bridge: Intel Corporation 5000 Series Chipset FSB Registers (rev 12)
00:11.0 Host bridge: Intel Corporation 5000 Series Chipset Reserved Registers (rev 12)
00:13.0 Host bridge: Intel Corporation 5000 Series Chipset Reserved Registers (rev 12)
00:15.0 Host bridge: Intel Corporation 5000 Series Chipset FBD Registers (rev 12)
00:16.0 Host bridge: Intel Corporation 5000 Series Chipset FBD Registers (rev 12)
00:1c.0 PCI bridge: Intel Corporation 631xESB/632xESB/3100 Chipset PCI Express Root Port 1 (rev 09)
00:1d.0 USB controller: Intel Corporation 631xESB/632xESB/3100 Chipset UHCI USB Controller #1 (rev 09)
00:1d.1 USB controller: Intel Corporation 631xESB/632xESB/3100 Chipset UHCI USB Controller #2 (rev 09)
00:1d.2 USB controller: Intel Corporation 631xESB/632xESB/3100 Chipset UHCI USB Controller #3 (rev 09)
00:1d.7 USB controller: Intel Corporation 631xESB/632xESB/3100 Chipset EHCI USB2 Controller (rev 09)
00:1e.0 PCI bridge: Intel Corporation 82801 PCI Bridge (rev d9)
00:1f.0 ISA bridge: Intel Corporation 631xESB/632xESB/3100 Chipset LPC Interface Controller (rev 09)
00:1f.1 IDE interface: Intel Corporation 631xESB/632xESB IDE Controller (rev 09)
00:1f.2 IDE interface: Intel Corporation 631xESB/632xESB/3100 Chipset SATA IDE Controller (rev 09)
01:00.0 PCI bridge: Intel Corporation 80333 Segment-A PCI Express-to-PCI Express Bridge
01:00.2 PCI bridge: Intel Corporation 80333 Segment-B PCI Express-to-PCI Express Bridge
02:0e.0 RAID bus controller: Dell PowerEdge Expandable RAID controller 5
04:00.0 PCI bridge: Broadcom EPB PCI-Express to PCI-X Bridge (rev c3)
05:00.0 Ethernet controller: Broadcom Corporation NetXtreme II BCM5708 Gigabit Ethernet (rev 12)
06:00.0 PCI bridge: Intel Corporation 6311ESB/6321ESB PCI Express Upstream Port (rev 01)
06:00.3 PCI bridge: Intel Corporation 6311ESB/6321ESB PCI Express to PCI-X Bridge (rev 01)
07:00.0 PCI bridge: Intel Corporation 6311ESB/6321ESB PCI Express Downstream Port E1 (rev 01)
07:01.0 PCI bridge: Intel Corporation 6311ESB/6321ESB PCI Express Downstream Port E2 (rev 01)
08:00.0 PCI bridge: Broadcom EPB PCI-Express to PCI-X Bridge (rev c3)
09:00.0 Ethernet controller: Broadcom Corporation NetXtreme II BCM5708 Gigabit Ethernet (rev 12)
10:0d.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] ES1000 (rev 02)

If there is any more information that is required, please just request it and I will provide it.

A:

This morning I decided to run some more debug tests and I found that when I ran MTR, it returned an error about DNS resolving(a tiny error message in the top left). I set my DNS nameservers to 8.8.8.8 (Google) and the IP of our router - in that order(Google then router) and the internet speed shot up to the usual speeds. 
The reason this issue did not occur on Windows, is due to the fact that by habit, I naturally set the first nameserver to 8.8.8.8 on Windows machines, however not for Linux.
I hope this helps anyone else who may encounter this issue.

