Cisco Cisco IOS Software Release 12.2(27)SBC
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MPLS VPN—Inter-AS—IPv4 BGP Label
Distribution
Distribution
This feature enables you to set up a Virtual Private Network (VPN) service provider network so that the
autonomous system boundary routers (ASBRs) exchange IPv4 routes with Multiprotocol Label
Switching (MPLS) labels of the provider edge (PE) routers. Route reflectors (RRs) exchange VPNv4
routes by using multihop, multiprotocol, External Border Gateway Protocol (EBGP). This configuration
saves the ASBRs from having to store all the VPNv4 routes. Using the route reflectors to store the
VPNv4 routes and forward them to the PE routers results in improved scalability.
autonomous system boundary routers (ASBRs) exchange IPv4 routes with Multiprotocol Label
Switching (MPLS) labels of the provider edge (PE) routers. Route reflectors (RRs) exchange VPNv4
routes by using multihop, multiprotocol, External Border Gateway Protocol (EBGP). This configuration
saves the ASBRs from having to store all the VPNv4 routes. Using the route reflectors to store the
VPNv4 routes and forward them to the PE routers results in improved scalability.
The MPLS VPN—Inter-AS—IPv4 BGP Label Distribution feature has the following benefits:
•
Having the route reflectors store VPNv4 routes results in improved scalability—This configuration
scales better than other configurations where the ASBR holds all of the VPNv4 routes and forwards
the routes based on VPNv4 labels. With this configuration, route reflectors hold the VPNv4 routes,
which simplifies the configuration at the border of the network.
scales better than other configurations where the ASBR holds all of the VPNv4 routes and forwards
the routes based on VPNv4 labels. With this configuration, route reflectors hold the VPNv4 routes,
which simplifies the configuration at the border of the network.
•
Enables a non-VPN core network to act as a transit network for VPN traffic—You can transport IPv4
routes with MPLS labels over a non MPLS VPN service provider.
routes with MPLS labels over a non MPLS VPN service provider.
•
Eliminates the need for any other label distribution protocol between adjacent LSRs—If two
adjacent label switch routers (LSRs) are also BGP peers, BGP can handle the distribution of the
MPLS labels. No other label distribution protocol is needed between the two LSRs.
adjacent label switch routers (LSRs) are also BGP peers, BGP can handle the distribution of the
MPLS labels. No other label distribution protocol is needed between the two LSRs.
•
Includes EBGP multipath support to enable load balancing for IPv4 routes across autonomous
system (AS) boundaries.
system (AS) boundaries.
Feature History for MPLS VPN—Inter-AS—IPv4 BGP Label Distribution
Release
Modification
12.0(21)ST
This feature was introduced.
12.0(22)S
This feature was implemented on the Cisco 12000 series routers (for
specific line cards supported, see
specific line cards supported, see
) and integrated into Cisco IOS
Release 12.0(22)S.
12.0(23)S
Support was added for the Cisco 12000 Series Eight-Port OC-3c/STM-1c
ATM Line Card (8-Port OC-3 ATM) and the Cisco 12000 Series Three-Port
Gigabit Ethernet Line Card (3-Port GbE).
ATM Line Card (8-Port OC-3 ATM) and the Cisco 12000 Series Three-Port
Gigabit Ethernet Line Card (3-Port GbE).
12.2(13)T
This feature was integrated into Cisco IOS Release 12.2(13)T.