Hi, since version 2.1.2.0 is new I would like to share couple things from my experience upgrading from code 1.3.3.x to code 2.1.2.0. Chances are that this post will save someone some time because this information is not documented in upgrade guide.
Basically at the moment in order to do upgrade from early version to 2.1 code you as a first step need to open TAC case which will give you a link to complete software access form. To complete this form you need CLI access to your system because you will have to run some commands which will result is special ID of your system which you put on this form. Process is relatively easy and explained well on form. After that it may take few days before BU will approve your request on back end. You will know that it was approved because in System Settings > Upgrades you will start seeing message which is telling you that you can go to code 2.1.
In according to upgrade guide process is simple - two clicks process. After first click you wait 30 sec, and after second click you wait 4-6 hours even if message will tell you 2-3 hours. This is easy part -just plan accordingly.
Here are confusing part #1 - right before upgrade will start message will tell you something like "Upgrade to 1.5.208". This is fine because this is what code 2.1.2.0 is.
Confusing part #2 - during upgrade process system stay on 56 present message for few hours. Little scary - just wait longer or don't look until 6 hours will pass.
Confusion part #3 - after upgrade done you login to GUI and don't see 2.1 GUI. Then you look in System About page and see message that you are on code 1.3.3.5 - Wow. Basically this is normal for this phase of upgrade since UI package was not yet upgraded - only core components are running on 2.1 at this point. So, do not pay attention and do not panic.
Confusing part #4 - after upgrade users which login via AD authentication will work, but local admin users will not work. This is expected because some things made more secure inside. To fix this SSH to any DNAC server and run command
"rbac external_auth_fallback enable" (If you have multiple servers you only need to run command on one server. This should fix admin account login back to GUI.
Confusion part #5 - after these 6 hours you are not done yet. This was phase 1 - system core upgrade. Now you need to upgrade application packages - this will take another hour for downloads and another few hours for application upgrades. Until you do this your DNA will fail on pretty much everything because it is not supposed to work in this mode.
So, save yourself time and proceed with second phase of upgrade immediately after you done with first phase. It is interesting to mention that you don't need to do backup in the middle, because you anyway will not be able to return to this point because this is intermediate point. If you will ever need to rollback you should rollback to previous code, so make sure you did backup before started first phase of upgrade.
Steps in 2nd phase of upgrade are also very simple - go to System Settings > Upgrades and click to download all software packages. After download is completed click on Upgrade and wait for hours. In our case phase 2 took 4.5 hours.
TAC is saying that during upgrade you can SSH to server and run command "maglev package status" - during normal work this command will show you packages information and will say version and which one is deployed or not. During upgrade I had issues with stability of this command because it runs via UI API and required GUI credentials, so it kept asking me to give her my GUI admin account and password, but every 10 sec it experienced reset. So, I couldn't really successfully run it during upgrade - only after upgrade was completed.
Good luck.
