Disadvantage of VPNs
The disadvantages of VPN are related to implementation troubleshooting trust and internet availability.
a.Implementation can be time consuming: Implementation a VPN can sometimes be difficult and time consuming. Configuration planning, management of keys, and troubleshooting can easily turn what seen to be a simple task into weeks of labour.
b.Troubleshooting Problems Because in a VPN data enters a gateway unlevered and leaves the gateway encrypted it can be very difficult to troubleshoot a VPN problems such as key resynchronization failures in authentication dropped packets and gateway load and stress can all make pinpointing problems in the VPN a difficult task.
To make your VPN reliable make sure the VPN administrators clearly understand the underlying software architecture and a thorough understanding of internet protocols.
c.Vendor Interoperability: Many vendors offering VPN solutions long with the complex nature of VPN protocols such as IP sec it can be difficult to get different vender solution to interoperate. The first step in attempting to connect two vendors. VPN devices is to checks the VVPN web site and check for your vendor interoperability. The second thing to do is to make sure you have the configuration right between the two.