Selective Vrf Download; Line Card Roles And Filters In Selective Vrf Download - Cisco ASR 9000 Series Configuration Manual

Selective VRF Download

and replace private AS Numbers from AS Path in BGP feature allows routers that belong to a private AS to
access the global Internet. A network administrator configures the routers to remove private AS numbers from
the AS path contained in outgoing update messages and optionally, to replace those numbers with the ASN
of the local router, so that the AS Path length remains unchanged.
The ability to remove and replace private AS numbers from the AS Path is implemented in the following
ways:
• The remove-private-as command:
• The replace-as command replaces the private AS numbers being removed from the path with the local
The feature can be applied to a neighbor in the address family configuration mode. Therefore, if you apply
the feature for a neighbor in an address family, only the outbound update messages are impacted.
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
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
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◦ Removes private AS numbers from the AS path even if the path contains both public and private
ASNs.
◦ Removes private AS numbers even if the AS path contains only private AS numbers. There is no
likelihood of a 0-length AS path because this command can be applied to eBGP peers only, in
which case the AS number of the local router is appended to the AS path.
◦ Removes private AS numbers even if the private ASNs appear before the confederation segments
in the AS path.
AS number, thereby retaining the same AS path length.
in different VRFs)
Implementing BGP
http://www.cisco.com/
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