EVPN-MPLS: Non-revertive preference-based DF election

You can configure non-revertive preference-based designated forwarder (DF) election for an Ethernet segment identifier (ESI) in an Ethernet VPN-MPLS (EVPN-MPLS) network. By default, preference-based DF election for an Ethernet segment identifier (ESI) is revertive, which means:

• If the EVPN provider edge (PE) device currently in the DF role goes down, the next preferred PE device becomes the new DF.
• When the old DF comes back up, the DF role reverts to the old DF.
• Changing the current DF role for an ESI frequently can impact traffic flow. To avoid revertive DF role changes, you can now set the non-revertive option at the [edit interfaces name esi df-election-type preference] hierarchy level.
• We also provide new options you can configure to load-balance DF election per EVPN instance (EVI) or per ESI based on the lowest configured preference value or the highest configured preference value, as follows:
• At the EVI level-Use the designated-forwarder-preference-least option or the designated-forwarder-preference-highest option at the [edit routing-instances evpn-instance-name protocols evpn] hierarchy level.
• At the ESI level-Use the least option at the [edit interfaces interface-name esi df-election-type preference] or [edit protocols evpn interconnect esi df-election-type preference] hierarchy level.