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CHAPTER
16-1
Cisco ASR 901 Series Aggregation Services Router Software Configuration Guide
OL-23826-09
16
Configuring MPLS VPNs
A Virtual Private Network (VPN) is an IP-based network that delivers private network services over a
public infrastructure. VPNs allow you to create a set of sites that can communicate privately over the
Internet or other public or private networks.
Contents
• Understanding MPLS VPNs
• Configuring MPLS VPNs
• Configuration Examples for MPLS VPN
Understanding MPLS VPNs
A conventional VPN consists of a full mesh of tunnels or permanent virtual circuits (PVCs) connecting
all of the sites within the VPN. This type of VPN requires changes to each edge device in the VPN in
order to add a new site. MPLS VPNs, also known as Layer 3 VPNs, are easier to manage and expand
than conventional VPNs because they use layer 3 communication protocols and are based on a peer
model. The peer model enables the service provider and customer to exchange Layer 3 routing
information, enabling service providers to relay data between customer sites without customer
involvement. The peer model also provides improved security of data transmission between VPN sites
because data is isolated between improves security between VPN sites.
The Cisco ASR 901 supports the following MPLS VPN types:
• Basic Layer 3 VPN—Provides a VPN private tunnel connection between customer edge (CE)
devices in the service provider network. The provider edge (PE) router uses Multiprotocol Border
Gateway Protocol (MP-BGP) to distribute VPN routes and MPLS Label Distribution Protocol (LDP)
to distribute Interior Gateway Protocol (IGP) labels to the next-hop PE router.
• Multi-VRF CE—Multi-VRF CE extends limited PE functionality to a CE router in an MPLS-VPN
model. A CE router now has the ability to maintain separate VRF tables in order to extend the
privacy and security of an MPLS-VPN down to a branch office rather than just at the PE router node.
Note Cisco ASR 901 does not support VRF on TDM interfaces.