Airport slows down when anybody uses VPN through it

airportvpn

I have a MBP with OSX 10.7.3, from which I use a VPN connection (Cisco IPSec) to login on my company network. That in itself is not a problem.

I also have an Airport Extreme (version 7.6.1) as the backbone of my home network using ADSL to my ISP. That in itself is not a problem, either.

But the combination of the two is a major problem for everybody in the house. Especially those that play online games…

Whenever I connect to the company network, I can see the ping latency go from 20 ms to 600 ms for the ADSL leg. And is not just from my machine, but for every machine in the house. Which should mean the problem is in the Airport.

I have of cause been looking at all the usual sites, but cannot find anything similar reported before…

Without the VPN connection:

traceroute to dr.dk (195.137.194.128), 64 hops max, 52 byte packets
1  10.0.1.1  3.293 ms  0.784 ms  0.693 ms
2  nn.nn.nn.nn  19.489 ms  18.837 ms  23.681 ms
3  ...

With the VPN connection:

traceroute to dr.dk (195.137.194.128), 64 hops max, 52 byte packets
1  10.0.1.1  2.515 ms  0.553 ms  2.898 ms
2  nn.nn.nn.nn  688.489 ms  650.996 ms  690.190 ms
3  ...

So the question is: Does anybody know what is going on here? Do you know of any solution? E.g. should I downgrade the Airport software?

Best Answer

It's more than likely the bandwidth used by your VPN rather than the Airport itself.

My work VPN connection with a corporate laptop used to use a lot of bandwidth, I'd notice other stuff slowing down considerably. Maintaining links to the domain servers, a VOIP client, and all of the other things installed on there used a lot of resources.

When I stopped using a corporate laptop and connected my personal laptop through a web based SSL VPN with terminal services instead, things improved a lot as it was only basically screen sharing rather than uploading and downloading actual files and data.

Unless you can set-up a proxy and monitor the usage of each device, you're not really going to find out how much bandwidth each device is using, but it's unlikely to be the VPN itself, or the Airport at fault, just the bandwidth used by what's being transferred over the VPN.

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