L3 VPN basics

Why we need L3 VPN ?

Traditional L3 networs have some issues all customers must implement a separate ip address range which is not feasible solution, or use nat but natting also have some limitations and is not a scalable solution also some of the applications does not work with nat.


L3 VPN or vprn allows multiple customer sites to commumicate at the ip level over a provider managed mpls network.
The provider network remains a shared infrastructure offering services to multiple customers.and it also isolates the routing and packet forwarding of a particular customer.

Each provider router maintains separate forwarding table for each vprn sessions.

It appears to the customers that there routers are connected as L3 routers, the SP domain is transparent to the customers.

VPRN Benefits

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customer routes

The service provider manages the core network and the

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the provider core

Customers receive the redundancy benefits designed into

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Frame Relay)

Security is similar to existing layer 2 technologies (ATM or

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at customer sites

Layer 2 independent - allows different layer 2 connectivity

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between different customersAllows the usage of overlapping private IP address space

Simplifies the routing topology at customer sites:- The routing topology is simplified as the provider is managing the routed infrastructure, the customer might only have the static routes and reap the benefits.