What is manual configuration techniques ?

Only a person knows the "Key".
The person himself manually installs the "Key" into all devices on which IPSec works.
It is very simple techniques.

But the techniques are not scalable.
Because a person has to install the "Key" into all devices,
before using IPSec.
whenever a new device is added to the network.
whenever a lifetime of secret keys expires.
This techniques are practical in small, static environments.

   For example, a company could create a VPN using IPsec in gateways at several sites.
   If the number of sites is small, and if a administrator manages all the sites.
   This is likely to be a feasible context for manual techniques.