Slow VPN throughput speeds using WRT54GX4

Question

I have a WRT54GX4 and am experiencing slow VPN throughput.
When I connect from my home network to my work network via my companies VPN client I've noticed that the throughput drops significantly.  Speed tests to DSL Reports are ~10500 kbit/s download and 950 kbit/s upload when going through the WRT54GX4 not using VPN, but only 250 kbit/s download and 95 kbit/s upload when I connect using my VPN client.
I have used the same laptop computer at various locations away from home and tested through my work VPN connection to DSL Reports and noted that the speeds don't change too much when I switch between direct and VPN.
Next I bypassed the WRT54GX4 router all together and connected directly to my cable modem at home and repeated the test.  This time the speed test using my VPN client was ~9950 kbit/s download and 850 kbit/s upload.
My company has several DS-3 connections that are load sharing and as mentioned above testing from other locations has shown that my office isn't the bottleneck.
Everything points to the WRT54GX4.
Also, my previous router was an early Wireless-G Linksys router - forgot the model - and it did not slow down my VPN like this new one does.
The problem exists in either wired or wireless connection mode.
I recently upgraded with the latest firmware V 1.00.20 but that didn't help.
I have also tried various MTU sizes and auto but nope, no joy there.
By the way, we have both Cisco and Nortel VPN servers at work and I've tried each client on two separate host machines at home and both exhibit the same slow connection.
When I turn off the VPN client everything is great and my speeds are super.
Any ideas?

Answer 1

This may help significantly.
I have DSL, speed is 3 mb. I have a WRT54GS router. When I hardwired the connection from modem to laptop, speed was 3mb - ISP was doing it's job. Via wireless connection, speed dropped to 1 mb.
I spoke with Linksys and after some tweaks (upgrading Firmware etc ...) - they said that the drop was not unexpected and this is what I had to accept.
I spoke with my network specialist at work (I am in I.T. myself) and he thought that the router should not eat 2/3 of the speed. This was confirmed by the Geek Squad as well.
Combing through this forum, I came across an interesting article about some tweaks you can do with www.speedguide.net - they have an optimzing tool that has yielded the solution.
Try this ...
http://www.speedguide.net/files/TCPOptimizer.exe
This will download the tool. When you open this up you will see a number of tabs - the general tab yielded the most for me. You will see some radio buttons for current state and proposed state. When you choose apply you will see the registry settings that will be affected - a re-boot is necessary.
So after I did this, I noticed that my wireless speed was up to 2 mb - better but still only 2/3 of what I expected.
About an hour later I went to the basement, did a speedcheck ( www.speedtest.net ) - and I was getting 3 mb!! I went up to the kitchen and ... 3mb. I went to the access point and ... 3mb.
Bottom line: Re-boot helps - but it seems that there is some cycling involved ... so try a little later.
Message Edited by Shamrockoz on 11-09-2007 01:44 PM