Thanks so much Robert for your help!
Unfortunately, there is no respond from the email address you provided.
I've been contacting Meraki support in order to get the required info for RADIUS attribute Files: (RADIUS VSA Name/ Attribute Type) and vendor ID for Meraki MR
We are going for live deployment in two days; and I can't risk it if the AVAYA IDE RADIUS doesn't accept Cisco vendor for Meraki.
This is the last message from Meraki support :
" think you'll probably have to create a custom device template in the Avaya IDE. I haven't tested with any of this so I can only try to point you in the right direction.
You should know that for dynamic VLAN assignment and group policy assignment Meraki expects the RADIUS server to use any of these four fields (you can configure which one it's actually sending):
https://yuzje69629.i.lithium.com/t5/image/serverpage/image-id/8709iB0E81EC5044A9F05/image-size/large...
The following page also provides details about these from a numeric perspective:
https://community.cisco.com/t5/security-documents/ise-network-access-attributes/ta-p/3616253#toc-hId...
See if you can figure out a way to have Avaya IDE send one of these."
and
"I don't think Meraki has its own Vendor ID. As I posted before it integrates nicely with third party RADIUS servers and works with multiple fields from multiple vendors. You just need to configure which field your RADIUS is going to send to the authenticators (in this case the APs)."