4.1.b Implement and troubleshoot basic MPLS L3VPN

4.1.b [i] L3VPN, CE, PE, P

Multiprotocol Label Switching (MPLS) was originally derived from Tag Switching, and various other vendor methods of IP-switching support enhancements in the scalability and performance of IP-routed networks by combining the intelligence of routing with the high performance of switching.

MPLS is now used for VPNs, which is an appropriate combination because MPLS decouples information used for forwarding of the IP packet (the label) from the information carried in the IP header.

MPLS VPNs can combine any of the following:

● Globally unique and routable addresses

● Globally unique, non-routable addresses

● Private addresses (RFC1918)

● Addresses that are neither globally unique nor private.

Label Switched Paths are bound to VPN-IP routes and are confined to the VPN Service Provider.

P Router or Provider Router is a Label Switch Router (LSR) that functions as a transit router of the core network. A Provider Edge router (PE router) is a router between one network service provider’s area and areas administered by other network providers.

The customer edge (CE) is the router at the customer premises that is connected to the provider edge of a service provider IP/ MPLS network. CE peers with the Provider Edge (PE) and exchanges routes with the corresponding VRF inside the PE. The routing protocol used could be static or dynamic (an Interior Gateway Protocol like OSPF or an Exterior Gateway Protocol like BGP).

Adam, Paul (2014-07-12). All-in-One CCIE V5 Written Exam Guide (Kindle Locations 4427-4430).  . Kindle Edition.