Introduction to VPN (Virtual Private Network)
Let’s start with the definition. VPN is a logical network and created over shared physical infrastructure.
Shared infrastructure can be private such as MPLS VPN of a Service Provider or over the Public infrastructure such as Internet.
There are many concepts to understand VPN in detail but in this article I will cover the definition, common design considerations, and some not well known concepts about it.
We can group VPNs into two categories. WAN and the Datacenter VPN Technologies.
WAN VPN Technologies
2.mGRE (Multipoint GRE)
8. MPLS L3 VPN
Datacenter VPN Technologies
1.EoMPLS (Ethernet over MPLS (a.k.a VPWS)
2. VPLS (Virtual Private Lan Service)
3. OTV (Overlay Transport Virtualization)
6. VXLAN (And other host based overlays such as NVGRE, STT, GENEVE)
Of course this is not the complete list. Please note that some of the technologies which I grouped into WAN technologies can be used in the Datacenter and vice versa.
For example LISP can be used in Datacenter as well and VPWS and VPLS can be used on the Wide Area Network as well.
I am going to cover each of these technologies in the individual article so please stay tuned and follow the website by subscribing the email list. Also please know that there is a video lesson which I explain all these technologies in my Self Paced CCDE Course in detail.
VPN Design Considerations
For better illustration, imagine customer is receiving a Layer 2 MPLS VPN service from the Service Provider. In Overlay VPN model, endpoints are the customer devices, which is called as CE (Customer Equipment).
MPLS Layer 3 VPN is a Peer to Peer technology. In Peer to Peer model, customer has a routing neighborship with the Service Provider. Endpoints are not the customer sites in this model. One side of the VPN is a customer device (CE) and remote end is Service Provider device (PE).
Some VPNs require tunnel as well. For example although I didn’t include in the list above but MPLS Traffic Engineering is used as a VPN mechanism and requires a tunnel. This doesn’t mean that there is no encapsulation and decapsulation in MPLS Traffic Engineering, of course there is, but it requires tunnel as well. Or GRE requires a tunnel and encapsulation (IP header is encapsulated in GRE header).
For example MPLS Traffic Engineer tunnels don’t support routing protocol,since the MPLS-TE LSPs (Label Switch Paths) are unidirectional which mean Head-end and Tail-end routers are not associated and not bidirectional.
All WAN technologies except IPSEC and LISP in our list supports routing protocols.
VPN Choice Check List
Is there any Layer 8 and above issue ?
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