Version 4.1 - 1.10 VPNs
For this section, I'm going to just touch briefly on the types of VPNs. Actual configuration or specifics of how they operate should be covered in section 6.6 with the VPN clients covered in 5.9.
LAYER 2 VPNs
* MPLS L2 VPN - Multiprotocol Label Switching
* VPWS - Virtual Private Wire Service also see PWE3 - Pseudo Wire Emulation Edge to Edge
* 802.1q Tunneling
* EVPN
* Frame Relay (old)
* ATM (old)
LAYER 3 VPNs
* IPsec - Point to Point
* MPLS/BGP L3 VPN
Note that MPLS can be either L2 or L3. A Layer 2 vpn allows "devices to communicate with each other as they would when connected to a common LAN segment." L2 VPNs are on the same segment. In L3 VPN connections, each side of the connection is on a different subnet.
MPLS - The most important concepts here are the label operations of swap, push and pop. Don't forget the implicit null signals PHP - Penultimate Hop Popping. In addition to the routing table, there is an LFIB for the labels.
VRF - Virtual Routing and Forwarding. I have experience with vrfs in a production environment. This part shouldn't be hard. It creates a separate routing and forwarding instance. Don't forget about the RD (Route Descriptors) X:Y.
Tag Switching - This was listed in the blueprint. Really? Tag Switching is just the old Cisco-proprietary TDP which was replaced by the standards-based LDP - in MPLS.
And that finishes up VPNs. Of course there is much more to say about VPNs, but that will be covered later. I'm done with this one.