16-33
ATM Switch Router Software Configuration Guide
OL-7396-01
Chapter16 Configuring Tag Switching and MPLS
MPLS VPNs
Each Fast Ethernet interface can be linked with only one Enhanced ATM router module interface.
However, more than one Fast Ethernet interface can be linked with the same Enhanced ATM router
module.
MPLS VPNs
This section describes how to configure MPLS VPNs on the ATM switch router.
When used with MPLS, the VPN feature allows several sites to interconnect transparently through a
service provider network. One service provider network can support several different IP VPNs . Each of
these networks appears to the users as a private network, separate from al l other networks. Within a VPN,
each site can send IP packets to any other site in the same VPN.
Each VPN is associated with one or more VPN routing or forwarding instances (VRFs). A VRF consists
of an IP routing table, a derived Cisco express forwarding (CEF) table, a nd a set of interfaces that use
this forwarding table.
The ATM switch router maintains a separate routing and CEF table for each VRF. This prevents
information being sent outside the VPN and allows the same subnet to be used in several VPNs without
causing duplicate IP address problems.
For additional MPLS configuration documentation, refer to the sources in Table 16-10.
This section describes how to configure MPLS VPNs on Fast Ethernet and ATM interfaces. By linking
the interface to an enhanced ATM router module interface, tag switching can be enabled on the interfaces
and they can be part of a VPN Network. The enhanced ATM Router Module (ARM) serves as the MPLS
Table16-10 Additional MPLS VPN Configuration Documentation
Document URL
MPLS Virtual Private
Networks
http://www.cisco.com/univercd/cc/td/doc/product/software/ios120
/120newft/120t/120t5/vpn.htm
MPLS VPN over ATM: with
OSPF on the Customer Side
(with Area 0)
http://www.cisco.com/warp/public/121/mpls_ospf2.html
MPLS VPN over ATM: with
OSPF on the Customer Side
(without Area 0)
http://www.cisco.com/warp/public/121/mpls_ospf1.html
Configuring VPN MPLS over
ATM with Cisco 7500 Routers
and LightStream 1010
Switches
http://www.cisco.com/warp/public/121/vpn-mpls.html
MPLS VPN over ATM
Networks Configuration
Examples
http://www.cisco.com/univercd/cc/td/doc/product/vpn/solution/m
anmpls/overview/configat.htm