EX3400 upgrade path

EX 3400, enterprise environment.

We have about 150 of this model, not replacing them just yet. Higher ups are hearing the bell ringing about old code.

Many are on 12.X, some on 15.X

A few on 18.X, a couple on 21.x

I’m not finding a comprehensive page outlining our exact “supported version“ steps (lower than 20.x), to bring them all closer to updated. Some 3400 may get licensed for Mist, to join our Mist-enabled 4100 corral of current. (Replacing all 3300 & older)

Juniper resource of the day states the supported versions for the 3400 begin at 20.2R3.

I need to turn assumptions of upgrade steps into facts, for field upgrades on production switches;

V 12 – –> V 15

V 15 – –> V 18

V 18.2R1 – –> V 20.2R3 , where current support and Mist licensing ability would begin.

I just bench-flashed a few for standby w v18,v20,v23

Insights?