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.
Selective VRF Download Disable
Selective VRF Download (SVD) functionality is disabled, by default. To enable SVD, configure the svd
platform enable command in administrative configuration mode and reload the chassis using the reload
location all command. To disable SVD that is already enabled, use the no svd platform enable command
and reload the chassis using the reload location all command.
Calculating Routes Downloaded to Line Card with or without SVD
The number of routes that will be downloaded to the line card with or without selective VRF download option
can be calculated by following the Total Tables and Routes Downloaded by Line Card Type table below.
This table summarizes the total routes and tables downloaded on the line cards of each SVD card type. Savings
can be calculated by the difference between the numbers in the Without SVD row.
Table 2: Total Tables and Routes Downloaded by Line Card Type
Routes DownloadedTables DownloadedCard Type
(o+Y)R(o+Y)Customer
nxRnCore
nRnWithout SVD
•
n is the total number of VRFs present
Cisco ASR 9000 Series Aggregation Services Router Routing Configuration Guide, Release 5.1.x
OL-30423-03 59
Implementing BGP
Selective VRF Download Disable
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