Since you are using Veeam 11a I am going to guess it will not be supported and you will need to upgrade to at least the latest release of v12.  v11 is out of support so you should upgrade to at least v12 now.  With v13 early release of the VSA it will not be long before the full GA comes for Windows and remaining installs.

Hi ​@lev.goronshtein , 

Since backups are running against vCenter - no, it won’t matter

If you want to leverage the plugin however in Veeam then it will matter.  See this forum thread - AOS 7.3 - R&D Forums

You need the 7.1 plugin.  But again if you are not using this plugin it will work.

Thank you ​@kira.bezhanova  and ​@Chris.Childerhose 

Also is 11a or 11.x EOL?

v11 supports Esxi 7.0 update 3: https://helpcenter.veeam.com/archive/backup/110/vsphere/platform_support.html

But indeed, v11 has end of support for almost 2 years

all of them :) https://www.veeam.com/product-lifecycle.html 

It has been end of support for almost 2 years now.  You should really consider upgrading.

thank you both