Cisco NCS 6000 Series Configuration Manual page 435

Implementing Routing Policy
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
end-policy
vrf vrf-export
Allocate-Label
The allocate-label attach point provides increased control based on various attribute match operations. This
attach point is typically used in inter-AS option C to decide whether the label should be allocated or not when
sending updates to the neighbor for the IPv4 labeled unicast address family. The attribute setting actions
supported are for pass and drop.
Retain Route-Target
The retain route target attach point within BGP allows the specification of match criteria based only on route
target extended community. The attach point is useful at the route reflector (RR) or at the Autonomous System
Boundary Router (ASBR).
Typically, an RR has to retain all IPv4 VPN routes to peer with its PE routers. These PEs might require routers
tagged with different route target IPv4 VPN routes resulting in non-scalable RRs. You can achieve scalability
.
.
.
if destination in (172.16.1.0/24) then
set extcommunity rt (10:101)
set weight 211
elseif origin is egp then
set local-preference 212
set extcommunity rt (10:101)
endif
set extcommunity rt (10:111222) additive
address-family ipv4 unicast
export route-policy bgpvrf-export
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.
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Routing Configuration Guide for Cisco NCS 6000 Series Routers, IOS XR Release 6.4.x
Export
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