Broadband speed down to a third through router - why? and can I do anything about it?

[exexpat]

Non-geeky person here - please help! I finally got round to getting a wireless router last week, mainly to save arguments over the summer holidays when DS wants to watch something on iPlayer and DD hasn't had her daily Club Penguin fix (and so that I don't have to queue to use the computer for MN important emails).

Main computer is a fairly new desktop, plugged into Virgin cable broadband through an ethernet cable. I have a 20Mbps package, and when I test it, I do actually get 19Mbps or higher. But when I plug the wireless router in, the speed goes down to around 6Mbps - this is even though the main computer is still connected via an ethernet cable to the modem via the router, not wirelessly, and when nothing else is using the wireless connection. Do routers normally slow down the connection that much, and is there anything I can do to improve it?

Do you have wireless encryption? If not, someone else be using your connection.

Does this question mean anything to you-

what is your IP address when you're connected to the modem directly, and what is it when you're connected via the router?

Thanks - werewolf - security is enabled, so no-one else could be using it without a password.

prism - I know what an IP address is, but don't know how to check it. Is it easy to find out? I'm on Windows 7 and Firefox, if that helps.

Bring up a DOS/Command prompt and enter:
ipconfig

What is that going to show though?

The Router is going to add some overhead, but I'm surprised at how much effect it seems to be having.

Hmm. I'm a Mac person and can't remember how to do this in W7- maybe someone will pop up here and tell you how to do it. The reason I'm asking is to see if you have the problem of "Double-NATting" where your modem is doling out IP addresses with what's called Network Address Translation, and the router is doing it too (the router is likely to be set up that way). This can cause a lot of slowdown, and if you find your IP address is, say, 192.168.1.2 when you're on the modem and 10.0.0.8 when you're on the router, this could be the source of the problem.

If you can get into the router settings and find a bit that says "enable bridge mode", this will turn off NAT and you can see if it helps. Before doing this make sure you know how to reset your router to factory settings, as this is the easiest way to undo bridge mode (it is usually done by pressing a special switch somewhere when you turn the thing on).

I'm sorry about these relatively baffling suggestions but I don't think it's going to be a geek-free solution...

Aha. Someone did. Whaddaya reckon, BP? Double NAT, or maybe MTU?

The ipconfig suggestion above will do the trick.

Wouldn't you still want the Wireless Router to do NATing though so it would allow multiple devices to connect to it and share it's single connection to the modem?

If anything should be in bridge mode shouldn't it be the modem as that's the thing that will only ever have the one thing plugged into it (the wireless router).

That said though are the costs of double NATing really that high?

Oh and thinking some more I don't know if a computer can easily tell if it's being double NAT'ed as that's all being dealt with by the router above it.

So won't all a local ipconfig will tell you is what IP address the computer has been assigned by the router above it?

And that's quite likely to be the same whether it's the modem or the wireless router handing them out (192.168.x.x).

You won't know if that IP address is one (modem only) or two NATs (modem and then the wireless router) away from the "actual" IP address of the cable modem.

Double Natting doesn't always cause trouble, but it can, and although a lot of devices are set to use the 192.168.1.XXX format, a lot aren't (I think Netgears (or is it Belkins) always use 192.168.2.XXX, for instance, and loads start with 10.X), so seeing what the difference is when removing the router is likely to tell you if you effectively have 2 DHCP servers on your network (not a good idea!).

I suppose you could use the modem in bridge mode, but the router would be OK as well, as it would enable the devices to get their IP addresses from the modem, and then behave as if it wasn't there.

This may indeed be a red herring but I thought it would be a start. I mean, the router is obviously adding something that buggers it up, and extra-dhcp-serving might be it?

Or the MTU.

Thanks Prism and Badger - I think I just about followed that, but it's getting a bit technical for me and I'm not sure I'd be able to reverse things if I changed settings and made it worse.... but in the meantime Virgin have sent me another router (I had bought one, not realising that apparently I get one free by upgrading to the 20mbps package) so I will try installing that and see if I have the same problem. And if I do, perhaps the Virgin tech support people will be able to talk me through the various things to try. Thanks anyway . I may be back with some more detailed questions if I hit another wall....

Yeah- aren't you glad you asked?! I can't honestly think of anything that would cause it that isn't rather nerdy to deal with. But telling me what your IP addresses are when on the modem and router might help.

Good luck, EEP.

The new router works . The main computer still has 19mbps or so, and when I use the netbook upstairs it gets 6mbps so that is fine by me. Don't know what is different about this one - the set-up procedure was much the same - but as long as it works I'm happy. Now, does anyone want to take a nearly-new Cisco router off my hands?

Aha. If you'd said it was a Cisco... they are way more complicated than real people need. Put it on eBay.

You may be able to spee up the netbook by changing the wireless mode (once upon a time there was a, then b, now g and N) to suit your netbook better. But to be honest I wouldn't bother if it works.