TABLE OF CONTENTS Now that we have seen the composition of the major types of MPLS VPNs, let s have a look at some practical details of implementation. Applications vary from vendor to vendor, but there are generally three to four steps involved in establishing a Layer-3 VPN.
The steps to establishing an L3 VPN are as follows:
Establish the core MPLS Network.
Establish the MPLS tunnel.
Create and map policies.
Test and monitor.
The following application example was provided by gracious permission of Riverstone Networks.
RSVP-TE initiates the required tunnels through the core network to interconnect the required points of presence. Using any of the methods supported by RSVP-TE, explicitly routed with resource reservations or hop-by-hop, creates these tunnels. Once these tunnels link the edge routers, policy on the ingress router is used to classify and map the inbound traffic to a specific tunnel. All layer 2 information is stripped, and the native IP packet is encapsulated in the MPLS label for the specified tunnel and forwarded accordingly (see Figure 7.36).
The policy statements on the ingress MPLS router use information in the protocol header to classify inbound packets into an FEC. Policy is not limited to the ability to classify purely on source or destination IP address. Classification can look deep into the header information to include Source Socket, Destination Socket, Protocol, and Type of Service, as well...
