{"draft":"draft-ietf-bess-evpn-pref-df-13","doc_id":"RFC9785","title":"Preference-Based EVPN Designated Forwarder (DF) Election","authors":["J. Rabadan, Ed.","S. Sathappan","W. Lin","J. Drake","A. Sajassi"],"format":["HTML","TEXT","PDF","XML"],"page_count":"17","pub_status":"PROPOSED STANDARD","status":"PROPOSED STANDARD","source":"BGP Enabled ServiceS","abstract":"The Designated Forwarder (DF) in Ethernet Virtual Private Networks\r\n(EVPNs) is defined as the Provider Edge (PE) router responsible for\r\nsending Broadcast, Unknown Unicast, and Multicast (BUM) traffic to a\r\nmultihomed device\/network in the case of an All-Active multihoming\r\nEthernet Segment (ES) or BUM and unicast in the case of Single-Active\r\nmultihoming. The Designated Forwarder is selected out of a candidate\r\nlist of PEs that advertise the same Ethernet Segment Identifier (ESI)\r\nto the EVPN network, according to the default DF election algorithm.\r\nWhile the default algorithm provides an efficient and automated way\r\nof selecting the Designated Forwarder across different Ethernet Tags\r\nin the Ethernet Segment, there are some use cases where a more\r\n\"deterministic\" and user-controlled method is required. At the same\r\ntime, Network Operators require an easy way to force an on-demand\r\nDesignated Forwarder switchover in order to carry out some\r\nmaintenance tasks on the existing Designated Forwarder or control\r\nwhether a new active PE can preempt the existing Designated Forwarder\r\nPE.\r\n\r\nThis document proposes use of a DF election algorithm that meets the\r\nrequirements of determinism and operation control. This document\r\nupdates RFC 8584 by modifying the definition of the DF Election\r\nExtended Community.","pub_date":"June 2025","keywords":["Highest-Preference","Lowest-Preference","Non-Revertive","Don\u2019t Preempt","Preemption"],"obsoletes":[],"obsoleted_by":[],"updates":["RFC8584"],"updated_by":[],"see_also":[],"doi":"10.17487\/RFC9785","errata_url":null}