We have constructed and tested the vpn connection between windows vpn client and dd-wrt router in article ''How to set a vpn connection between dd-wrt and windows OS", and now some further tests have also been completed and will be introduced in this article.
As we know, dd-wrt could work as the vpn server and client. Except the windows vpn client, there are two other options for client which are dd-wrt router and ATA with vpn client. We choose xia302 with pptp client to construct the vpn connection for small voip system as follows:

We have introduced how to set dd-wrt, and then configure the pptp client in xia302(details of setting could be found in user manual which is available in our "Downloads"). our setting is shown as follows:

click"ok", then the connection will be going on...

Well. the connection has set up


If all go well, the xia302 will be found in dd-wrt:

Based on the network with xia302 pptp client, we have tested the capability of the vpn in the voip system. Result is satisfying, the connection between pptp client and server is stable, and the connection supports 10 concurrent calls.
If you would like to choose l2tp to be the protocol of your vpn connection, then the Jin310 should be a good choice. The construction of vpn with Jin310 l2pt client is shown as follows:

Also we have tested the performance of this kind of vpn. Actually there are a bit differences between two networks. But the differences between protocols themselves should be noted, and how to choose depends on your care.
For connections above, we use dd-wrt vpn router as a vpn server, dd-wrt router can be also used as a vpn client to access small company or call shop.xia304 with dd-wrt is a good option to work as a vpn client:

The capability of VOIP VPN is mainly depends on the vpn server. The cost of vpn router, what we used is less than $100 in above networks. The conclusion can be reached from the tests above: vpn could process more than 10 concurrent calls, and the data rate is more than 1Mpbs with about 100ms delay.

If you want to get more powerful vpn connection, it must expand the vpn server's capability:

1, buy vpn hardware. That would be very expensive.
2, try the linux or window vpn server base on x86 platform
3, find some vpn service provider.

TCS