The BSSID is derived from the AP MAC address, and incremented with every SSID. So if you know the first SSID, then if you add one, it will have one number higher.
If you want to know before provisioning any SSID, I found this reference on how the BSSID is calculated from the AP MAC address. I tried myself and it still seems to work:
If I check the bss-table for an AP '80008':
(MC1-7210) *#show ap bss-table | include 80008 18:64:72:7f:26:31 SSID-2 N/A 10.12.7.13 5GHz/VHT/80MHz 52E/21.0/23.0
18:64:72:7f:26:21 SSID-2 N/A 10.12.7.13 2.4GHz/HT/20MHz 1/11.0/19.5
18:64:72:7f:26:20 SSID-1 N/A 10.12.7.13 2.4GHz/HT/20MHz 1/11.0/19.5
18:64:72:7f:26:30 SSID-1 N/A 10.12.7.13 5GHz/VHT/80MHz 52E/21.0/23.0
18:64:72:7f:26:32 SSID-3 N/A 10.12.7.13 5GHz/VHT/80MHz 52E/21.0/23.0
18:64:72:7f:26:22 SSID-3 N/A 10.12.7.13 2.4GHz/HT/20MHz 1/11.0/19.5
18:64:72:7f:26:23 SSID-4 N/A 10.12.7.13 2.4GHz/HT/20MHz 1/11.0/19.5
18:64:72:7f:26:33 SSID-4 N/A 10.12.7.13 5GHz/VHT/80MHz 52E/21.0/23.0
And get the AP MAC address (also on the sticker on the AP):
(MC1-7210) *#show ap database long | include 80008
80008 AP-Group 335 10.12.7.13 18:64:72:cf:f2:62 CNBP000000
Now we can start the described procedure with that MAC address:
First Step: [Steps are taken from the example referenced, but that does not have the original AP MAC; The IN/OUT are added with a real-world example]
The controller takes the OUI and simply uses it as the first 6 characters of the BSSID 00:0b:86:
IN> 18:64:72:CF:F2:62
OUT> 18:64:72:xx:xx:xx
Second Step:
This is the interesting part. The controller first takes the next character and simply removes it. 6
The next character is then taken 6
A Boolean XOR is performed using this character and the value Hex 8, creating a new character E
IN> 18:64:72:CF:F2:62 -> CF => F => F XOR 8 => 7
OUT> 18:64:72:7x:xx:xx
Third Step:
At this point the controller takes the next 3 HEX characters from the MAC address (characters 9-11) 0:da:
These 3 characters are appended to the first 7 characters, and these are the first 10 characters of the BSSID 00:0b:86:E0:da:
IN> 18:64:72:CF:F2:62
OUT> 18:64:72:7F:26:xx
Fourth Step:
If the AP has 2 Ethernet ports and 2 Radios, then each Radio will be capable of a total of 16 BSSIDs
The 2.4 GHz radio will use the last HEX character of the wired Ethernet port for it's 11th character 3
The 2.4 GHz radio will begin assigning HEX values starting at 0 and incrementing to F for the 12th and final character 00:0b:86:E0:da:30 through 00:0b:86:E0:da:3F
The 5 GHz radio will increment the last HEX character of the wired Ethernet port by 1, and use it for it's 11th character 4
The 5 GHz radio will begin assigning HEX values starting at 0 and incrementing to F for the 12th and final character 00:0b:86:E0:da:40 through 00:0b:86:E0:da:4F
IN> 18:64:72:CF:F2:62 => 2 + 1 => 3
OUT> 18:64:72:7F:26:3x
Results in BSSID Range: 18:64:72:7F:26:30 - 18:64:72:7F:26:3F
Which makes the first BSSID on 5GHz 18:64:72:7F:26:30, which matches the output of show ap bss-table.
No guarantees that this always works, but for me it did in this case.
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Herman Robers
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If you have urgent issues, always contact your Aruba partner, distributor, or Aruba TAC Support. Check
https://www.arubanetworks.com/support-services/contact-support/ for how to contact Aruba TAC. Any opinions expressed here are solely my own and not necessarily that of Hewlett Packard Enterprise or Aruba Networks.
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Original Message:
Sent: Jul 19, 2023 03:52 PM
From: the.sleeper
Subject: Is there anyway to know an AP's BSSID, before provisioning it?
Controller environment... we've decided we want add a label with the 5 Ghz BSSID on each AP we add to our network.
Wondering is there anyway to know an AP's BSSID, before provisioning it?
I know how to find it after its provisioned, but wonder if there's a way to know before. (Just to streamline the workflow)
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Russell
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