It is becoming increasingly common to stretch Ethernet Virtual Private Network (EVPN) services across Inter-Autonomous System (Inter-AS) boundaries. In such Inter-AS deployments, providers do not like to expose loopbacks of a provider edge (PE) router's loopbacks in one AS to the other AS, since this typically ensures less maintenance overhead and also allays security concerns. Inter-AS Option B for EVPN is ideally suited for such deployments as the next-hops of the EVPN routes for Inter-AS Option B are reset at the AS Border Router (ASBR), so the receiving AS does not know the loopback addresses of an advertising AS. This proposal provides a new technique to enable Inter-AS Option B for EVPN implementations that involves minimal configuration at ASBRs, which, in some instances, may enable multi-path and/or Prefix-Independent Convergence (PIC) -type load balancing at ASBRs.
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Mohanty, Satya; Mishra, Mankamana; and Sajassi, Ali, "OPTIMIZED MULTI-HOMING IN INTER-AS OPTION B FOR ETHERNET VIRTUAL PRIVATE NETWORKS", Technical Disclosure Commons, (January 24, 2022)