Administrator Guide

Dynamic Route Leaking
Route Leaking is a powerful feature that enables communication between isolated (virtual) routing domains by segregating and
sharing a set of services such as VOIP, Video, and so on that are available on one routing domain with other virtual domains.
Inter-VRF Route Leaking enables a VRF to leak or export routes that are present in its RTM to one or more VRFs.
Dynamic Route Leaking 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 filter out leaked routes while sharing global routes with VRFs.
Configuring Route Leaking without Filtering Criteria
You can use the ip route-export tag command to export all the IPv4 routes corresponding to a source VRF. For leaking
IPv6 routes, use the ipv6 route-export tag command. This action exposes source VRF's routes (IPv4 or IPv6 depending
on the command that you use) to various other VRFs. The destinations or target VRFs then import these IPv4 or IPv6 routes
using the ip route-import tag or the ipv6 route-import tag command respectively.
NOTE: In Dell EMC Networking OS, you can configure at most one route-export per VRF as only one set of routes can
be exposed for leaking. However, you can configure multiple route-import targets because a VRF can accept routes from
multiple VRFs.
After the target VRF learns routes that are leaked by the source VRF, the source VRF in turn can leak the export target
corresponding to the destination VRFs that have imported its routes. The source VRF learns the export target corresponding to
the destinations VRF using the ip route-import tag or ipv6 route-import tag command. This mechanism enables
reverse communication between destination VRF and the source VRF.
If the target VRF contains the same prefix (either sourced or Leaked route from some other VRF), then the Leak for that
particular prefix will fail and an error-log will be thrown. Manual intervention is required to clear the unneeded prefixes. The
source route will take priority over the leaked route and the leaked route is deleted.
Consider a scenario where you have created four VRF tables VRF-red, VRF-blue, VRF-Green, and VRF-shared. The VRF-shared
table belongs to a particular service that should be made available only to VRF-Red and VRF-Blue but not VRF-Green.
For this purpose, routes corresponding VRF-Shared routes are leaked to only VRF-Red and VRF-Blue. And for reply, routes
corresponding to VRF-Red and VRF-Blue are leaked to VRF-Shared.
For leaking the routes from VRF-Shared to VRF-Red and VRF-Blue, you can configure route-export tag on VRF-shared (source
VRF, who is exporting the routes); the same route-export tag value should be configured on VRF-Red and VRF-blue as
route-import tag (target VRF, that is importing the routes). For a reply communication, VRF-red and VRF-blue are configured
with two different route-export tags, one for each, and those two values are configured as route-import tags on VRF-shared.
To configure route leaking, perform the following steps:
1. Configure VRF-shared using the following command:
ip vrf vrf-shared
interface interface-type slot/port
ip vrf forwarding vrf-shared
ip address ip—address mask
A non-default VRF named VRF-Shared is created and the interface 1/4 is assigned to this VRF.
2. Configure the export target in the source VRF:.
ip route-export 1:1
3. Configure 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.
4. Configure the import target in VRF-red.
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Virtual Routing and Forwarding (VRF)