White Papers

Previous FTOS releases support static route leaking, which enables route leaking through static commands. Dynamic Route Leaking,
introduced in the 9.7(0.0) release, enables a source VRF to share both its connected routes as well as dynamically learnt routes from various
protocols, such as ISIS, OSPF, BGP, and so on, with other default or non-default VRFs.
You can also leak global routes to be made available to VRFs. As the global RTM usually contains a large pool of routes, when the
destination VRF imports global routes, these routes will be duplicated into the VRF's RTM. As a result, it is mandatory to use route-maps to
lter out leaked routes while sharing global routes with VRFs.
Conguring Route Leaking with Filtering
When you initalize route leaking from one VRF to another, all the routes are exposed to the target VRF. If the size of the source VRF's RTM
is considerablly large, an import operation results in the duplication of the target VRF's RTM with the source RTM entries. To mitigate this
issue, you can use route-maps to lter the routes that are exported and imported into the route targets based on certain matching criteria.
These match criteria include, prex matches and portocol matches.
You can use the match source-protocol or match ip-address commands to specify matching criteria for importing or exporting
routes between VRFs.
NOTE: You must use the match source-protocol or match ip-address commands in conjunction with the route-map command to
be able to dene the match criteria for route leaking.
Consider a scenario where you have created two VRF tables VRF-red and VRF-blue. VRF-red exports routes with the
export_ospfbgp_protocol route-map to VRF-blue. VRF-blue imports these routes into its RTM.
For leaking these routes from VRF-red to VRF-blue, you can use the ip route-export route-map command on VRF-red (source VRF, that is
exporting the routes); you must also specify a match criteria for these routes using the match source-protocol command. When you leak
these routes into VRF-blue, only the routes (OSPF and BGP) that satisfy the matching criteria dened in route-map
export_ospfbgp_protocol are exposed to VRF-blue.
While importing these routes into VRF-blue, you can further specify match conditions at the import end to dene the ltering criteria based
on which the routes are imported into VRF-blue. You can dene a route-map import_ospf_protocol and then specify the match criteria as
OSPF using the match source-protocol ospf command.
You can then use the ip route-import route-map command to import routes matching the ltering criteria dened in the
import_ospf_protocol route-map. For a reply communication, VRF-blue is congured with a route-export tag. This value is then congured
as route-import tag on the VRF-Red.
To congure route leaking using ltering criteria, perform the following steps:
1 Congure VRF-red:
ip vrf vrf-red
interface-type slot/port
ip vrf forwarding VRF-red
ip address ip—address mask
A non-default VRF named VRF-red is created and the interface is assigned to this VRF.
2 Dene a route-map export_ospfbgp_protocol.
Dell(config)route-map export_ospfbgp_protocol permit 10
3 Dene the matching criteria for the exported routes.
Dell(config-route-map)match source-protocol ospf
Dell(cong-route-map)match source-protocol bgp
This action species that the route-map contains OSPF and BGP as the matching criteria for exporting routes from vrf-red.
Virtual Routing and Forwarding (VRF)
1061