Technical Overview

There are two main components in an MPLS VPN backbone, the customer routing and forwarding tables maintained on the provider (edge) routers, and the underlying mechanism used to transport customer traffic. When a customer data packet arrives on the ingress service provider edge router, it is encapsulated with a MPLS (VPN) label that corresponds to the best route in the appropriate customer routing and forwarding table. Then it is forwarded over an MPLS label switched path (LSP) to the egress service provider edge router. Alternatively, MPLS VPN traffic may be tunneled over a non-MPLS network using IP or GRE, L2TPv3, or IP/IPSec.

An understanding of both components is essential for fast and effective troubleshooting of MPLS ...

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