Cisco ASR 9000 Series Routing Configuration Guide

Use show bgp neighbors and show bgp update-group commands to verify that the that private AS numbers
were removed or replaced.
Selective VRF Download
Selective VRF Download (SVD) feature enables the downloading of only those prefixes and labels to a line
card that are actively required to forward traffic through the line card.
To meet the demand for a consolidated edge MSE platform, the number of VRFs, VRF interfaces, and the
prefix capacity increase. Convergence timings differ in different line card engines. One of the major factors
that determine convergence timing is the time taken to process and program a prefix and its associated data
structures. A lesser number of prefixes and labels ensure better convergence timing. By enabling selective
download of VRF routes, SVD increases scalability and reduces convergence problems in Layer 3 VPNs
(L3VPNs).
For more information on selective VRF download, see the Cisco white paper, Selective Virtual Routing and
Forwarding Table Download: A solution to increase Layer3 VPN scale at this URL http://www.cisco.com/
en/US/technologies/collateral/tk648/tk365/white_paper_c11-681649.html
Line Card Roles and Filters in Selective VRF Download
In a selective VRF download (SVD) context, line cards have these roles:
•
Core LC: a line card that has only core facing interfaces (interfaces that connect to other P/PEs)
•
Customer LC: a line card that has one or more customer facing interfaces (interfaces that connect to CEs
in different VRFs)
The line cards handle these prefixes:
•
Local Prefix: a prefix that is received from a CE connected to the router in a configured VRF context
•
Remote Prefix: a prefix received from another PE and is imported to a configured VRF
These filters are applicable to each line card type:
•
A core LC needs all te local prefixes and VRF labels so that the label or IP forwarding, or both is set up
correctly.
•
A customer LC needs both local and remote prefixes for all the VRFs to which it is connected, and for
other VRFs which some connected VRFs have dependency. This is based on the import/export RT
configuration; VRF ‘A’ may have imported routes from VRF ‘B’, so the imported route in VRF ‘A’ points
to a next-hop that is in VRF ‘B’. For route resolution, VRF ‘B’ routes need to be downloaded to each
line card that has a VRF ‘A’ interface.
•
If a line card is hosts both core facing and customer facing interfaces, then it does not need to do any
filtering. All tables and all routes are present on such line cards. These line cards have a role called
“standard”. All RPs and DRPs have the standard role.
•
To correctly resolve L3VPN routes, the IPv4 default table needs to be present an all nodes. However,
if the line card does not have any IPv6 interface, it can filter out all IPv6 tables and routes. In such a
case, the line card can be deemed “not interested” in the IPv6 AFI. Then it behaves as if IPv6 is not
supported by it.
Cisco ASR 9000 Series Aggregation Services Router Routing Configuration Guide, Release 5.3.x
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Implementing BGP
Selective VRF Download

Cisco ASR 9000 Series Specifications

General

Brand	Cisco
Model	ASR 9000 Series
Category	Network Router
Language	English