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I got my CCENT and working on ICND2 to get my CCNA. I am stuck on this topic and am unable to grasp the context. WAN and VPN and how they differentiate. My understanding is we need WAN for "Physical" connectivity between different locations so we can connect our private LAN's in addition to go out to the internet. With just a WAN link, all we can do is just go out to the internet or if we have a routing protocol set up we can ping each routers public IP addresses.

Then with VPN we use that existing WAN setup to create a virtual network so that our private traffic generated from our LAN's can communicate and exchange info. For example a user in the local office is retrieving a file from a private server on the Corporate office, this action is not possible just with a WAN link and a VPN is needed. Am I getting it right? Is WAN alone just for public traffic and VPN allows private traffic over our public WAN. Basically what can I do with just a WAN link and what can I do with just A VPN and do we almost always need both working together. Thanks for your help!

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Originally, WANs were mostly defined by specific layer 1/2 protocols (Frame Relay, HDLC, SONET, etc) that they used, but Ethernet has taken over, and the others are rapidly fading into history. The term "WAN" now generally describes a network that covers some larger geographical area than a LAN. Sounds vague? It is.

Some WANs, like the Internet are public, but others are private, supplied by service providers. A company, for example, may purchase a private WAN to connect their various offices. In that case, the company has exclusive use of the WAN.

VPNs are used when you need to make a "virtual" private connection over a non-private network. The Internet is the most common use (since Internet connectivity is usually cheaper than private WANs), but you can have VPNs connecting subgroups within a private WAN.

If you understand tunnels, then VPNs are just another type of tunnel. MPLS VPNs are private WANs built upon a service providers network. The service provider ensures that your endpoints never communicate with another entity's endpoints. IPsec VPNs use encryption to protect the data and to authenticate the endpoints.

  • "MPLS VPN" is the modern marketing term for what WANs used to be. P2P and P2MP links today are very publicly done with MPLS, vs. the "who knows" methods of years long past. (frame, atm, various circuit emulations, etc. customers generally never knew, or cared how pt. A gets to pt. B. now that everything is ethernet (IP), MPLS, VRF, and VLANs are the "it" technologies) – Ricky Beam Mar 5 at 2:24

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