Are you doing split tunneling for the VPN clients?
If you are tunneling everything, then you can use the filter option on the concentrator to create filter so that you allow only a specific network.
Here is an example on how to create a filter.
http://www.cisco.com/en/US/tech/tk59/technologies_configuration_example09186a0080094eac.shtml
you need to follow instructions from 1 to 4.
Let me know how it goes.
Rate this post, if it helps.
Cheers
Gilbert
