preference (DF Election)
Syntax
preference {
least;
non-revertive;
value value;
}Hierarchy Level
[edit dynamic-profiles name interfaces name esi df-election-type],
[edit dynamic-profiles name logical-systems name interfaces name esi df-election-type],
[edit interfaces name esi df-election-type]
Description
Configure the preference-based election algorithm for the designated forwarder (DF) for an Ethernet segment among the multihoming provider edge (PE) devices in an Ethernet VPN (EVPN) network.
Configure all the candidate devices within the Ethernet segment with the same election algorithm. In the event of a mismatch between the locally configured DF election algorithm and the remote PE's DF election algorithm, all the PEs revert to the default DF election as specified in RFC 7432.
When configured, the device uses the value as an administrative preference value associated with the Ethernet segment identifier (ESI) you configure at the same ESI hierarchy level. The DF candidate devices exchange the preference value and the Don’t Preempt (DP) bit in EVPN Type 4 routes using the DF election extended community.
When the candidate devices in the Ethernet segment receive the Type 4 route, they determine their DF preference order based on the configured preference value, the DP bit, and the IP address.
The preference-based DF election process uses the highest configured preference value by
default. Configure the least option to enable DF election for the ESI
based on the lowest configured preference value. You can also set the preferred
preference level for the EVPN instance (EVI) using the
designated-forwarder-preference-highest or
designated-forwarder-preference-least statements at the [edit
routing-instance routing-instance-name protocols evpn] hierarchy.
The configuration at the EVI level takes precedence over the ESI level. You can use the
configurations at the EVI and ESI levels together to configure load balancing for the
DF.
The non-revertive option prevents a higher priority PE from preempting
the DF role from a lower priority PE after recovering from a failure, thus avoiding a
service impact caused by an additional DF role change. However it does not prevent role
changes due to administrative actions such as changing the DF preference
value.
Options
| least |
Enable the DF election for the ESI based on the lowest configured preference value. |
| non-revertive |
Don't allow DF Election preemption after a DF failure. This option does not
prevent role changes due to administrative actions such as changing the DF
preference |
| value |
The preference value for this DF election candidate device. If all of the DF candidate devices for the ESI have the same configured preference value they elect the DF based on the lowest IP address.
|
Required Privilege Level
interface—To view this statement in the configuration.
interface-control—To add this statement to the configuration.
Release Information
Statement introduced in Junos OS Release 17.3 for MX Series Routers with MPC and MIC interfaces.
least and non-revertive statements introduced in Junos
OS Release 24.2R1.