C 144.4.4.0/24 Direct, Te 1/1/4/1 0/0 00:32:36Important Points to Remember• If the target VRF conatins the same prefix as either the sourced or Leaked route from some other VRF, then route Leaking for thatparticular prefix fails and the following error-log is thrown.SYSLOG (“Duplicate prefix found %s in the target VRF %d”, address, import_vrf_id) withThe type/level is EVT_LOGWARNING.• The source routes always take precedence over leaked routes. The leaked routes are deleted as soon as routes are locally learnt by theVRF using other means.• For recovery, you must take appropriate action either by deleting the unwanted prefixes or issuing clear command or both.• In the target VRF, you cannot leak routes that are imported through the route leaking feature.• The leaked route points to the next-hop of the source routes. You cannot do any modifications to the next-hop of the leaked route inthe destination VRF.• IPv6 link local routes will never be leaked from one VRF to another.Configuring Route Leaking with FilteringWhen 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 RTMis considerablly large, an import operation results in the duplication of the target VRF's RTM with the source RTM entries. To mitigate thisissue, you can use route-maps to filter the routes that are exported and imported into the route targets based on certain matching criteria.These match criteria include, prefix matches and portocol matches.You can use the match source-protocol or match ip-address commands to specify matching criteria for importing or exportingroutes between VRFs.NOTE: You must use the match source-protocol or match ip-address commands in conjunction with the route-map command tobe able to define 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 theexport_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 isexporting the routes); you must also specify a match criteria for these routes using the match source-protocol command. When you leakthese routes into VRF-blue, only the routes (OSPF and BGP) that satisfy the matching criteria defined in route-mapexport_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 define the filtering criteria basedon which the routes are imported into VRF-blue. You can define a route-map import_ospf_protocol and then specify the match criteria asOSPF using the match source-protocol ospf command.You can then use the ip route-import route-map command to import routes matching the filtering criteria defined in theimport_ospf_protocol route-map. For a reply communication, VRF-blue is configured with a route-export tag. This value is then configuredas route-import tag on the VRF-Red.To configure route leaking using filtering criteria, perform the following steps:1 Configure VRF-red:ip vrf vrf-redinterface-type slot/port[/subport]ip vrf forwarding VRF-redip address ip—address maskVirtual Routing and Forwarding (VRF) 1021
