MPLS/VPN Architecture Overview

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Virtual routing and forwarding
While simple to deploy and appropriate for small to medium enterprises and shared data centers, VRF Lite does not scale to the size required by global enterprises or large carriers, as there is the need to implement each VRF instance on every router, including intermediate routers. This page was last edited on 24 April , at Only the VRF table associated with a customer site is consulted for packets from that site. Unsourced material may be challenged and removed. Each customer connection that is, each logical interface is associated with one VRF table. This table does not store routes received from directly connected CE routers. This is the historical explanation of the term VRF Lite:


Understanding Virtual Routing and Forwarding Tables

The overlay VPN model, most commonly used in a service provider network, dictates that the design and provisioning of virtual circuits across the backbone must be complete prior to any traffic flow.

In the case of an IP network, this means that even though the underlying technology is connectionless, it requires a connection-oriented approach to provision the service. From a customer's point of view, the Interior Gateway Protocol design is typically extremely complex and also difficult to manage. On the other hand, the peer-to-peer VPN model suffers from lack of isolation between the customers and the need for coordinated IP address space between them. With the introduction of Multiprotocol Label Switching MPLS , which combines the benefits of Layer 2 switching with Layer 3 routing and switching, it became possible to construct a technology that combines the benefits of an overlay VPN such as security and isolation among customers with the benefits of simplified routing that a peer-to-peer VPN implementation brings.

MPLS also adds the benefits of a connection-oriented approach to the IP routing paradigm, through the establishment of label-switched paths, which are created based on topology information rather than traffic flow. Unfortunately, that is not true. This is the same type of service that has already been described in the previous chapter. However, the mechanisms used to provision the service are different. This table is present only on PE routers. When a PE router receives a route from another PE router, it places the route into its bgp.

The route is resolved using the information in the inet. The resultant route is converted into IPv4 format and redistributed to all routing-instance-name. These routes are stored in the inet. PE-to-PE router connectivity must exist in inet. This enables the router to perform path selection and advertise from the bgp. To determine whether to add a route to the bgp. The backbone network is completely transparent to the customer equipment, allowing multiple customers or user communities to utilize the common backbone network while maintaining end-to-end traffic separation.

Routes across the provider backbone network are maintained using an interior gateway protocol — typically iBGP. IBGP uses extended community attributes in a common routing table to differentiate the customers' routes with overlapping IP addresses.

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Case Study: Virtual Private Networks in SuperCom Service Provider Network

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In IP-based computer networks, virtual routing and forwarding (VRF) is a technology that allows multiple instances of a routing table to co-exist within the same router at the same time. Because the routing instances are independent, the same or overlapping IP addresses can be used without conflicting with each other. VPN Routing and Forwarding Tables The overlapping addresses, usually resulting from usage of private IP addresses in customer networks, are one of the major obstacles to successful deployment of peer-to-peer VPN implementations. Virtual routing and forwarding (VRF) is a technology used in computer networks that allows multiple instances of a routing table to coexist within the same router at the same time. VRF partitions a router by creating multiple routing tables and multiple forwarding .