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Slow LAN using Router



hi, I'm new to this board.... :)

I've got a slight problem with my home network.

I've got a Windows 2003 Server, setup as a domain controller with DNS server setup. I have one workstation, running Windows XP Pro. I recently bought a US Robotics Broadband router so that I could share my NTL broadband connection between the 2 PCs without needing both PCs on (therefore ICS would be no good to me).

Anyway, browsing the web (WAN) from both PCs is perfectly fine... no problems... it's as fast as it shoudl be. The problem lies in the LAN. Copying from one machine to the other is unbelievably slow. It can take up to 5 minutes to copy around 35megabytes of information.

Does anyone have any ideas of what I should be looking for?

Also, if I browse to the workstation from the server using the workstations name (eg workstation1) it works fine and I can access it's shares and drives etc (although I have the slow problem I mentioned above), but if use the workstations IP address (eg it prompts me for a password, and whether I put in a domain password (Administrator) or a local user name/password that exists on the workstation, I cannot get access at all. It just says login failed.

Any ideas?

If you need more info, just ask.

Thanks in advance.



Also, I'm using Windows 2003 server as a Domain Controller with Active Directory/DNS as I want to enforce some very strict rules (policies) on the workstation machine as it is used by my children... who tend to click on things they shouldn't... their favourite is to somehow manage to drag files and folders into the recycle bin... quite regularly! :eek:
the the boardband router trying to perform any of the functions which you have 2k3 server doing? not sure maybe DHCP or something


The router is certainly doing DHCP functions, but the Win2k3 isn't running DHCP at all and all pc's on the network have static IP addresses registered with the router.
Maybe it's a speed/duplex setting thing on the network cards. It shouldn't be with a switch and all (in the router, right?), but it's worth checking.


It's all sorted now.

I connected my PCs to a hub and then connected that hub to a single port on the router and it's all lovely and fast now. Obviously the router isn't that great at sending LAN traffic between from one port to another. I guess that by using the hub the LAN data will just be travelling to one port on the hub and then going out the other port(s) to the other machines, and will be ignore by the router as the traffic is not for it. Anyway, it's all working smoothly now.

Thanks. :)
Strange. It should have worked better the other way around since the router has a switch on the LAN side. Switches normally make for less fuss than hubs.

Oh well, at least it's working. :)


What was strange was that when both PCs were plugged in to the router (without the hub) copying from the workstation to the server was very slow, but if you were on the workstation and you copied from something from the server it was quick (correct speed).

Very weird....



I think I've come up with a reason why my router was so slow at lan between my 2 pc's.

My internet account is through NTL. NTL check the MAC address of the network card, when that address changes you have to register your computer. It's an easy process, takes about a minute, but sometimes it can be a bit, errrmmm, iffy? :)

Anyway, my router (US Robotics) allows you to impersonate a MAC address so that the ISP doesn't realist you are now using a differnt piece of hardware. This worked fine and I didn't need to re-register my computer, etc. But I think this is what is causing my problem.

I have a server PC and a workstation one. The server one used to connect to the internet, so it's MAC address was the one that NTL knew about, so I got the router to clone that MAC address. Now, if I connect both computers to the router and copy a file from the workstation to the server, it's slow, but it's quick in the other direction: ie copying a file from the server to the workstation. I think this is to do with the fact that the router will have a list of MAC addresses that are on it, and it will have 2 entries for the servers MAC address, ie it will have an entry for port 1 (the actual server) and for the WAN port (connected to the NTL box). So I think it's somehow messing up in sending the data to both ports, or perhaps it is finding the WAN one first and detecting that it is a 10mbps (or 1mbps) connection and so sending the data to all ports with that MAC address at 10mbps rarther than 100mbps.

So, when I attach both computers to a switch, then attach that switch to the router it all works fine because the switch only knows about the 2 MAC addresses on its own ports. It detects what MAC address the data is for, finds that that address is one one of its own ports and that it's a 100mbps connection and sends the data straight there... the router never knows about the data cos the switch never sends it to the uplink port (connected to the router) for the router (or whatever) to deal with.

This would explain why it's quick in one direction, but not in the other.

Does anyone agree with this theory?

I could of course test it by stopping the router from cloning the mac address, connecting both PCs straight to the router, and seeing if the LAN speed increases, regardless of whether the internet access still works. In fact that is something I will try and do over the next couple of days.


One Step from The Edge
I need to understand something to be clear. Do you have a switch or a hub in the system with the router? This can make a difference eventually with speed sharing etc.
Yes, I agree with your analogy, mostly. I strongly believe that you need to disable your MAC cloning address on the router. Routing tables are bound via MAC addresses and their perspective IP's. When you are "talking" within your LAN, the MAC address will typically be used for resolution. If it cannot be found in the routing table then it may perform a broadcast to find the IP and then resolve for the MAC, thus storing the resolution in the routing table for later use. If you have two devices with the same MAC address on the same LAN, you will eventually run into problems in the resolution process.
If you are using a hub, not a switch, you will be sharing bandwidth at the hub. IE. 100MB hub while being used by two devices will share the 100MB throughput whereas the switch will give each device thier own 100MB throughput.
The slow one way could be a problem with the cloned MAC because the system may be resolving initally for the MAC, seeing two and then dumping the table and re-resolving via IP, thus becoming confussed, can't say without being in your system and watching the packets being exchanged.
The theory about resolving the MAC with the 10MB VS the 100MB card could infact be valid, seeing it first, especially if the MAC is the same as another and the IP address affiliated with that MAC is lower. This would typically be the order in which the system would "see" it, assuming both MAC's are identical.
My recommendation would be to just tweak your system layout by returning it back to the topology you had. Broadband to Router, all systems to router (without hubs, unless necessary). DHCP enabled on your router, using it's own MAC address, systems "obtaining IP via DHCP automatically". Of course you had it right by disabling the DHCP abilities on the server, can't have them both doing the same thing as you already know. Try to let the router do as much as possible in the default unless you really have a need to do otherwise, it seem to like that best.
Another great product to put on your system would be "Deep Freeze", it's relatively inexpesive and will let you put your drives into a state in which they will be "read only", even though it appears that everything is same as usaul. Once you "freeze" the drive(s) and re-boot the system, most everthing runs virtually or in RAM. If something changes that you want to "undo", just shutdown the system and re-boot. It will be exactly the way you left it. If you want to change stuff on the system, "thaw" the drive(s) and make changes the re-freeze.
try here http://www.deepfreezeusa.com/index.htm
Hope this helped, if not, give me an email and we'll "talk"

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