The import of BGP/EVPN routes is controlled by route target (RT) extended communities. A route is imported if it contains at least one RT that matches a locally configured import RT on the receiving router. The import and export RTs are automatically generated using the RFC-8365 algorithm, which includes the local BGP autonomous system (AS) as part of the calculated value.
In an external BGP (EBGP) peering session, since the routers reside in different ASs, the auto-generated RTs do not match, and routes are not imported. Currently, you can manually configure RTs on an EVPN instance to allow matching. For Auto-peering BGP sessions, as well as Type 5 EVPN routes, a common AS number in the private AS range is used in the auto-calculation to ensure matching. This feature provides support for “ignore-as” or also called “partial RT matching” functionality, which when enabled ignores the AS number portion of the RT when attempting to find a matching value. This reduces user configuration, since you do not have to use the CLI to create an EVPN instance with RTs, and also allows for easier interoperability with third-party devices in cases where ExtremeXOS auto-generates using the private AS.
For command information, see EVPN Commands.