In the EVPN Inline mode, MP-BGP sessions with the L2VPN EVPN address family are configured between tier-0 gateways and the external routers. The tier-0 gateway will negotiate the L2VPN EVPN AFI/SAFI with the external BGP peer (data center gateway) and start exchanging EVPN information. In this mode, the edge nodes are in the datapath between internal workloads and external networks.
The NSX-T EVPN Inline mode is based on the "Interface-less IP-VRF-to-IP-VRF Model" as defined in the IETF RFC9136. In this mode, the tier-0 gateway advertises to the data center gateway only Route Type 5 (RT-5) routes, that includes:
- Prefixes of segments connected directly to the tier-0 VRF gateway.
- Tier-1 segment prefixes redistributed to the tier-0 VRF gateway.
- Other redistributed sources, such as static routes and connected interfaces.
- BGP prefixes learned via southbound BGP sessions inside the VRF.
All routes received from and advertised to the data center gateways as RT-5 has an EVPN Router's MAC Extended Community with the MAC address of the corresponding peer uplink. Since "Interface-less IP-VRF-to-IP-VRF Model" is used, there is no recursive route lookup to resolve the RT-5 route. The packet is encapsulated in VXLAN using the RT-5's next hop as destination IP address and EVPN Router's MAC Extended Community as MAC address.
Inside the NSX domain, the control plane is still handled by the central control plane (CCP) and the encapsulation protocol among internal TEPs is still GENEVE.
