I am trying to configure cisco 877 ADSL router as vpn server , so that multiple site can login to cisco 877 ADSL router. Is it possible to achieve that. If so what is the procedure and if possible please copy the documentation URL here.
It is the same configuration on all IOS routers.
Here is sample configuration for IOS Easy VPN server and client in Network Extension mode:
The sample config uses local authentication, you can always change it to use radius authentication.