Cisco IOS PPTP server : PPP: Packet throttled, Dropping packet

If you get the following message on your Cisco router when you connect a VPN client using PPTP

*Mar 17 16:43:02.371: Vi5 PPP: Control packet rate limit 10 reached
*Mar 17 16:43:02.371: Vi5 PPP: Entering block state for 30 seconds
*Mar 17 16:43:02.371: Vi5 PPP: Packet throttled, Dropping packet 

Then it means you have an IOS version which greatly reduced the allowed rate of PPP control packets before it triggers a block.

Unfortunately, Windows 7 client sends packets at a rate that exceeds Cisco new default value. The result is that it takes 30 seconds (the default block duration) for the client to connect (yes, it connects successfully).

To fix this, you can change the rate threshold on the Cisco router by adding this line to your config:

ppp packet throttle 20 1 30 

It tells the router to accept up to 20 packets per 1 second, and block for 30 seconds if this rate is exceeded.