VPN???

Can someone tell me the pro's and con's of a VPN

Um... its good?

Seriously, what is the application or purpose you need to fill?, at least that way, we can look at why you need a VPN..etc..etc..

It allows a computer outside of your network access to your network as if it was physically on your network through a secure tunnel through the internet. Good for outside sales and anyone else that doesn't really need to take up space in your office (bosses).

Cons- you are letting someone's personal computer have access to your secure network. You have to make sure that person has loaded the proper security updates and make sure they have a firewall. For each person that connects to your VPN there is another doorway into your network for a hacker to try to get through, mainly on the client side and then through the client computer into your network. How sensitive is the data and how long can your company function without it worse case scenario?

Sometimes VPN's are used inside a LAN for people to access a certain part of your LAN that you don't want anyone to see, maybe accounting or the engineers depening on your business.

As EvilCabbage pointed out, it really depends on what you need it for. For example, my company uses VPNs to connect six offices to the corporate headquarters. From this perspective...

Pros:[list=1] [*]Inexpensive...hardware and ISP costs are tiny compared to data lines, direct dial, and some of the other methods that were used prior to VPN. [*]Easy to setup and maintain...usually a quick configuration of the IP addresses on each end of the tunnel and maybe a few encryption algorithms and away it goes.[*]Reappropriation of funds :D ...because we save so much money on dedicated lines and server equipment we are starting to upgrade all our offices to fiber connections for high speed internet.[/list=a]
Cons:[list=1][*]Reliant on internet...the internet goes down. We all know it. The most difficult part of having to support six VPN connections across the state is that I have to deal with four different ISPs and three different phone companies. When the internet goes down, so do the offices. And it's usually a lot of finger pointing from the ISPs and phone companies, until it magically starts working again. Of course, it's nobody's fault...you know what I'm saying.[*]Dedicated hardware...from my perspective this is really not a con, but I thought I would throw it in. You can setup VPNs through servers/workstations using Windows 2000, but you can also purchase VPN boxes that will control it for you. This is what we use, and I think they are relatively cheap for an office. Boxes like that usually have other functionality built in such as a firewall. The only reason I put this down as a con is that some people don't care for additional hardware, whether it is a small box or a dedicated VPN server.[/list=a]

These are the first points that come to mind. I might be able to give more information once you describe your needs. :)