Sample topology for VRF Route Sharing
Consider this sample topology which explains the VRF Route Sharing functionality in a hybrid cloud. In this sample topology, assume the Cisco Catalyst 8000V instance is deployed on the VM of the public cloud. Site A is an ACI deployment site, while Site B is the public cloud.
Leaf 1 and Leaf 2 form the Virtual Port Channel (vPC) pair for ACI. Both vPCs have different Route Distinguishers (RD). VRF1 and VRF2 are configured on the vPC pair for ACI. For example:
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VRF1 – RT:RT-EVPN-1, prefix:192.168.1.1
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VRF2 – RT:RT-EVPN-2, prefix:192.168.2.2
VRF3 and VRF4 are configured on the Cisco Catalyst 8000V instance. These two VRFs connect to the Voice Gateway (VGW). Each VRF uses a different Route Target (RT). For example:
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VRF3 – RT for EVPN: RT-EVPN-3, RT for IP BGP: RT-3, prefix:192.168.3.3
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VRF4 – RT for EVPN: RT-EVPN-4, RT for IP BGP: RT-4, prefix:192.168.4.4
In this topology, assume the BGP-EVPN fabric is present between the ACI and the Cisco Catalyst 8000V instance in the public cloud. The IP BGP protocol is used between the Cisco Catalyst 8000V instance and a cloud service provider, such as Microsoft Azure. The BGP-EVPN fabric redistributes the stitching routes between the EVPN and the IP BGP.
To enable the traffic flow between the ACI Site and the Public Cloud, both ACI and the Cisco Catalyst 8000V instance need to support VRF Route Sharing.
The Cisco Catalyst 8000V instance must be able to import the EVPN routes of VRF1 and VRF2 from ACI into VRF3 and VRF4. The IP BGP on the Cisco Catalyst 8000V side then redistributes the routes to the VGW in the public cloud.
Note
When the VTEP (VxLAN Tunnel Endpoint) IP and the RMAC (Route MAC addrress) are the same for two leafs, and the VNIC alone differs, theCisco Catalyst 8000V instance can forward the traffic across the tunnel.
Use cases
Using the same sample topology, here are the use cases for configuring VRF Route Sharing in a Cisco Catalyst 8000V instance:
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When VRF1 and VRF2 can talk to VRF3, but VRF3 and VRF4 cannot talk to each other.
vrf definition VRF3
rd 300:1
address-family ipv4
route-target export RT-EVPN-3 stitching
route-target import RT-EVPN-1 stitching
route-target import RT-EVPN-2 stitching
vrf definition VRF4
rd 400:1
address-family ipv4
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When VRF1 and VRF2 can talk to VRF3&4, but VRF3 and VRF4 cannot talk to each other.
vrf definition VRF3
rd 300:1
address-family ipv4
route-target export RT-EVPN-3 stitching
route-target import RT-EVPN-1 stitching
route-target import RT-EVPN-2 stitching
vrf definition VRF4
rd 400:1
address-family ipv4
route-target export RT-EVPN-4 stitching
route-target import RT-EVPN-1 stitching
route-target import RT-EVPN-2 stitching
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When VRF1 and VRF2 can talk to VRF3, but VRF3 and VRF4 can talk to each other.
vrf definition VRF3
rd 300:1
address-family ipv4
route-target export RT-EVPN-3 stitching
route-target import RT-EVPN-1 stitching
route-target import RT-EVPN-2 stitching
route-target export RT-3
route-target import RT-4
vrf definition VRF4
rd 400:1
address-family ipv4
route-target import RT-3
route-target export RT-4
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When VRF1 and VRF2 can talk to VRF3&4, but VRF3 and VRF4 can talk to each other.
vrf definition VRF3
rd 300:1
address-family ipv4
route-target export RT-EVPN-3 stitching
route-target import RT-EVPN-1 stitching
route-target import RT-EVPN-2 stitching
route-target export RT-3
route-target import RT-4
vrf definition VRF4
rd 400:1
address-family ipv4
route-target export RT-EVPN-4 stitching
route-target import RT-EVPN-1 stitching
route-target import RT-EVPN-2 stitching
route-target import RT-3
route-target export RT-4
For this use case, the Cisco Catalyst 8000V instance must configure EVPN on both VRF3 and VRF4.
Although IP BGP imports all the routes from VRF3 and VRF4, BGP does not advertise the imported routes of the VRF to the EVPN peer.
Note
Use the Stitching keyword in the configuration only when the sharing happens across the EVPN.