First of all we need to understand:-
1.How AutoUpdate feature works ?
The Autoupdate feature allows an AP to instruct an SM to perform a software upgrade.The AP examines
the current software version and FPGA versions on the SM to determine if an update is required, and
if required it gives the command to the SM to perform the appropriate update. In the background you configure AP with IP address of CNUT. That IP address in AP is considered as CNUT server IP address.
2.What is Network Accessibility Local ?
If you set Network accessibility to "local". That means the SM can be managed locally, But you can still access the SM from behind the AP by logging into AP and going to session status tab-->there you find LUID. This way you are accessing SM on layer 2 basis.
3.What is Network Accessibility Public ?
If you set the SM network accessibility as public. That means you can now access your SM from behind the AP with IP address or LUID of SM.Which means the GUI of SM will allow you to connect via layer 2 or layer 3 in this case.
If you have got what I informed above.Then your answer is there in user guide. Please read below captured paragraph 1(user guide) from user guide.Then read the same paragraph devided in 2 parts, for your reference I have made it simple in below paragraph 2 (explained)
Paragraph 1(user guide)
"SM Autoupdate is supported for SMs whose Network Accessibility parameter (in
the IP tab of the SM's Configuration management web page) is set to Local, not
Public. Even where Network Updater can discover SMs as children of their APs,
if their Network Accessibility is set to Public, then Network Updater must discover
them directly".
Paragraph 2 (explained devided in 2 parts)
"SM Autoupdate is supported for SMs whose Network Accessibility parameter (in
the IP tab of the SM's Configuration management web page) is set to Local not public".
Well this is one fact. Because when you set Network accessibility to local on your SM. That means command flow will be CNUT server to AP--->via Layer 3(IP address)
Then AP to SM--->via layer 2 (LUID). Now you will be thinking how ? Yes, so AP will act as virtual proxy between CNUT and SM.
"Even where Network Updater can discover SMs as children of their APs,if their Network Accessibility is set to Public, then Network Updater must discover them directly".
Well yes, in this case CNUT will communicate to SM directly via IP address (layer 3).
But believe me or not in all cases, if you are selecting AutoUpdate feature. The traffic and commands will pass through AP.And the AP will become transit path between CNUT server and SMs.
I hope this resolves your query and help you in future.
Regards,
Deepesh Chandra Sharma.
Technical Specialist-L3 Networks.
Cisco Certified Network Professional.
Cambium Certified over PMP/PTP/ePMP.