First of all a list my system specs:
Running a Samba Fileserver Version: 3.5.11
Network card: RTL8168 Gigabit with the correct Kernel Module from Realtek
Connected to a Gigabit Switch and Gigabit should be working
04:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168B PCI Express Gigabit Ethernet controller (rev 06)
Subsystem: ASUSTeK Computer Inc. P8P67 and other motherboards
Flags: bus master, fast devsel, latency 0, IRQ 43
I/O ports at e000 [size=256]
Memory at d0004000 (64-bit, prefetchable) [size=4K]
Memory at d0000000 (64-bit, prefetchable) [size=16K]
Capabilities: <access denied>
Kernel driver in use: r8168
Kernel modules: r8168
Settings for eth0:
Supported ports: [ TP ]
Supported link modes: 10baseT/Half 10baseT/Full
Supports auto-negotiation: Yes
Advertised link modes: 10baseT/Half 10baseT/Full
Advertised pause frame use: Symmetric Receive-only
Advertised auto-negotiation: Yes
Port: Twisted Pair
I'm not getting the transfer speeds I used to have. In the past I could connect my laptop with a Gigabit network card to the switch and reach transfer speeds from the Samba to Windows 7 machine of 60 MB/s which seems quite normal to me. This was with a larger MTU then the standard 1500.
However, when I now increase the MTU above 1500 the Samba fileserver cannot be reached, however an SSH session works without a problem! And, strangest of all, when I connect with laptop through the wireless I can also access the Samba server. However, the server is always connected wired.
Now, I can only get up to 20 MB/s with the standard 1500 MTU.
I don't have another Gigabit computer to test with. And the drivers on my Windows machine haven't changed.
I've been searching like crazy for the past few days to find the problem here.