Import; Export - Cisco ASR 9000 Series Routing Configuration Manual

Implementing Routing Policy

Import

The import attach point provides control over the import of routes from the global VPN IPv4 table to a
particular VPN routing and forwarding (VRF) instance.
For Layer 3 VPN networks, provider edge (PE) routers learn of VPN IPv4 routes through the Multiprotocol
Internal Border Gateway Protocol (MP-iBGP) from other PE routers and automatically filters out route
announcements that do not contain route targets that match any import route targets of its VRFs.
This automatic route filtering happens without RPL configuration; however, to provide more control over the
import of routes in a VRF, you can configure a VRF import policy.
The following example shows how to perform matches based on a route target extended community and then
sets the next hop. If the route has route target value 10:91, then the next hop is set to 172.16.0.1. If the route
has route target value 11:92, then the next hop is set to 172.16.0.2. If the route has Site-of-Origin (SoO) value
10:111111 or 10:111222, then the route is dropped. All other non-matching routes are dropped.
route-policy bgpvrf_import
if extcommunity rt matches-any (10:91) then
set next-hop 172.16.0.1
elseif extcommunity rt matches-every (11:92) then
set next-hop 172.16.0.2
elseif extcommunity soo matches-any (10:111111, 10:111222) then
pass
endif
end-policy
vrf vrf_import
address-family ipv4 unicast
import route-policy bgpvrf_import
.
.
.
'Set' is a valid operator for the 'med' attribute at the bgp import attach point.
Note

Export

The export attach point provides control over the export of routes from a particular VRF to a global VPN
IPv4 table.
For Layer 3 VPN networks, export route targets are added to the VPN IPv4 routes when VRF IPv4 routes are
converted into VPN IPv4 routes and advertised through the MP-iBGP to other PE routers (or flow from one
VRF to another within a PE router).
A set of export route targets is configured with the VRF without RPL configuration; however, to set route
targets conditionally, you can configure a VRF export policy.
The following example shows some match and set operations supported for the export route policy. If a route
matches 172.16.1.0/24 then the route target extended community is set to 10:101, and the weight is set to 211.
If the route does not match 172.16.1.0/24 but the origin of the route is egp, then the local preference is set to
212 and the route target extended community is set to 10:101. If the route does not match those specified
criteria, then the route target extended community 10:111222 is added to the route. In addition, RT 10:111222
is added to the route that matches any of the previous conditions as well.
route-policy bgpvrf_export
Cisco ASR 9000 Series Aggregation Services Router Routing Configuration Guide, Release 5.3.x
Attach Points
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