When enable-rr-vpn-forwarding or enable-inter-as-vpn is configured, only EVPN-MPLS routes are processed for label swap and the next hop is changed. EVPN-VXLAN routes are re-advertised without a change in the next hop.
The following shows how the router processes and re-advertises the different EVPN route types. For more information about the route fields, see the BGP-EVPN control plane for MPLS tunnels Guide.
Auto-discovery (AD) routes (type 1)
For AD per EVI routes, the MPLS label is extracted from the route NLRI. The route is re-advertised with Next-Hop-Self (NHS) and a new label. No modifications are made for the remaining attributes.
For AD per ES routes, the MPLS label in the NLRI is zero. The route is re-advertised with NHS and the MPLS label remains zero. No modifications are made for the remaining attributes.
MAC/IP routes (type 2)
The MPLS label (Label-1) is extracted from the NLRI. The route is re-advertised with NHS and a new Label-1. No modifications are made for the remaining attributes.
Inclusive Multicast Ethernet Tag (IMET) routes (type 3)
Because there is no MPLS label present in the NLRI, the MPLS label is extracted from the PMSI Tunnel Attribute (PTA) if needed, and the route is then re-advertised with NHS, with the following considerations:
For IMET routes with tunnel-type Ingress Replication, the router extracts the IR label from the PTA. The router programs the label swap and re-advertises the route with a new label in the PTA.
For tunnel-type P2MP mLDP, the router re-advertises the route with NHS. No label is extracted; therefore, no swap operation occurs.
For tunnel-type Composite, the IR label is extracted from the PTA, the swap operation is programmed and the route re-advertised with NHS. A new label is encoded in the PTA’s IR label with no other changes in the remaining fields.
For tunnel-type AR, the routes are always considered VXLAN routes and are re-advertised with the next-hop unchanged.
Ethernet-Segment (ES) routes (type 4)
Because ES routes do not contain an MPLS label, the route is re-advertised with NHS and no modifications to the remaining attributes. Although an ASBR or ABR re-advertises ES routes, EVPN multihoming for ES PEs located in different ASs or IGMP domains is not supported.
IP-Prefix routes (type 5)
The MPLS label is extracted from the NLRI and the route is re-advertised with NHS and a new label. No modifications are made to the remaining attributes.