Is it normal to see negative channel cost values?

[AnonymousM]

This is taken from an AP230 running 8.2r4:

Lowest cost channel: 120, lowest-cost: -1280
Channel 36 Cost: -1280
Channel 40 Cost: 1309
Channel 44 Cost: 792
Channel 48 Cost: 1055
Channel 52 Cost: 796
Channel 56 Cost: 279
Channel 60 Cost: 1039
Channel 64 Cost: 19
Channel 100 Cost: 793
Channel 104 Cost: 275
Channel 108 Cost: 23
Channel 112 Cost: 545
Channel 116 Cost: -1280
Channel 120 Cost: -1280
Channel 124 Cost: 0
Channel 128 Cost: 790
Channel 132 Cost: 23
Channel 136 Cost: 525
Channel 140 Cost: -1265
Channel 149 Cost: 783
Channel 153 Cost: 271
Channel 157 Cost: 10

Not all my AP230s look like this, but many do. I don't see this on any other model running any other HoveOS version.

Thank you.

[Victor31 · Accepted solution]

Yes, seeing negative channel cost values on Aerohive AP230 access points running HiveOS 8.2r4 is normal and expected behavior. These values are part of the Aerohive Channel Selection Protocol (ACSP), which automatically determines the best channel for the access point to operate on by evaluating factors such as interference, channel utilization, and regulatory restrictions. The channel cost is a metric used internally by ACSP, and a lower value including negative numbers indicates a better, more favorable channel. So, when you see values like -1280 for certain channels, it means those channels are currently optimal based on ACSP's assessment.

For example, in your case, channels 36, 116, and 120 all show a cost of -1280, meaning they are among the best choices for operation. It's also worth noting that a cost value of 32768 would mean a channel is being excluded from selection, possibly due to manual settings or DFS (Dynamic Frequency Selection) restrictions. If you notice that some AP230 units show different results than others, make sure they're running the same HiveOS version, as different firmware versions may affect how channel costs are calculated or displayed.

To know why certain costs are assigned, you can SSH into the access point and use the command show acsp channel-info detail, which gives a detailed breakdown of the cost factors for each channel.

[AnonymousM]

Hello Sam,

I uploaded the tech data to my case as requested.

[samantha_lynn]

I see you have a case open for this, would you be able to run the following debugs on the CLI of the AP, let the AP run as normal for 5 minutes, and then pull tech data and attach that to the case for review?

Debugs:

_kdebug wifi-driver wifi0 awemsglevel ascp

_kdebug wifi-driver wifi1 awemsglevel ascp

This guide reviews how to get tech data in HiveManager: https://thehivecommunity.aerohive.com/s/article/How-to-download-tech-data-in-HiveManager

[Macknkss]

Hi, I know this is old but we are seeing negative channel costs as well. Is this normal? Should I open a ticket with support? We have DFS enabled and I think it should be using one of those instead of the crowded channel 44. Thank you!

sh acs chann
wifi0 (14):
This interface did not finish scanning all available channels.

wifi1 (16):
State: RUN
Lowest cost channel: 44, lowest-cost: -39
Channel 36 Cost: -39
Channel 40 Cost: -25
Channel 44 Cost: -39
Channel 48 Cost: -24
Channel 52 Cost: -39
Channel 56 Cost: 57
Channel 60 Cost: -39
Channel 64 Cost: -11
Channel 100 Cost: -39
Channel 104 Cost: -39
Channel 108 Cost: 389
Channel 112 Cost: 375
Channel 116 Cost: -35
Channel 120 Cost: -39
Channel 124 Cost: -39
Channel 128 Cost: -39
Channel 132 Cost: -39
Channel 136 Cost: -39
Channel 140 Cost: -39
Channel 144 Cost: -39
Channel 149 Cost: -31
Channel 153 Cost: -39
Channel 157 Cost: -39
Channel 161 Cost: -24
Channel 165 Cost: -39

Interface Channel select state Primary channel Channel width Power ctrl state Tx power(dbm) Use Last Selection
--------- --------------------- ---------------- ------------- --------------------- ------------- ---------------------
Wifi0 Disable(Link down) Down 20 Disable(Link down) Down Channel:No Power:No
Wifi1 Enable 44 20 Enable 11 Channel:No Power:No
There is no ACSP information for radio (wifi2) in adsp sensor mode.
sh acs neig
wifi0(14) ACSP neighbor list (0/384):

wifi1(16) ACSP neighbor list (35/384):
Bssid Mode Ssid/Hive Chan Rssi(dBm) Aerohive AP CU CRC STA Channel-width VID NVID
bc96:e508:adb6 Access DADsTMOBILE 36 -88 no -- -- -- 80 - -
be96:e578:adb6 Access 36 -88 no -- -- -- 80 - -
bc30:7ebc:603c Access ClickShare-187172027... 36 -89 no -- -- -- 20 - -
40e1:e46b:dca3 Access Mami_Home 40 -92 no -- -- -- 80 - -
0e93:7c62:5f22 Access 44 -91 no -- -- -- 80 - -
08b4:b10d:041c Access Front Office Nest Ro... 149 -84 no -- -- -- 80 - -
9058:512a:a319 Access 157 -91 no -- -- -- 80 - -
9058:512a:a316 Access DASizemore 157 -91 no -- -- -- 80 - -
9058:512a:a31c Access 157 -92 no -- -- -- 80 - -
4c23:1a16:3534 Access CDE-PRIVATE 161 -81 yes 5 0 0 20 - -
4c23:1a16:3535 Access 161 -82 yes 3 0 0 20 - -
4c23:1a16:3536 Access CDE-CORP 161 -81 yes 5 0 0 20 - -
40e1:e46b:dca4 Access Mami_Home 161 -90 no -- -- -- 80 - -
52e1:e46b:dca4 Access 161 -89 no -- -- -- 80 - -
0693:970a:1b03 Access Keyes 44 -91 no -- -- -- 80 - -
1093:970a:1b03 Access 44 -91 no -- -- -- 80 - -
1c93:7c62:5f22 Access Lan Solo 44 -91 no -- -- -- 80 - -
1693:7c62:5f22 Access 44 -92 no -- -- -- 80 - -
0a93:7c62:5f22 Access xfinitywifi 44 -92 no -- -- -- 80 - -
1293:7c62:5f22 Access Xfinity Mobile 44 -91 no -- -- -- 80 - -
a498:13cf:8248 Access Journey 157 -92 no -- -- -- 80 - -
3485:84b0:a825 Access CDE-PRIVATE 48 -82 yes 3 0 0 20 - -
3485:84b0:a827 Access CDE-CORP 48 -82 yes 3 0 0 20 - -
3485:84b0:a828 Access Control-Rm-1C 48 -82 yes 3 0 0 20 - -
3485:84b0:a826 Access 48 -82 yes 0 0 0 20 - -
9058:512a:a31b Access 157 -91 no -- -- -- 80 - -
0ab4:b10d:041d Access 149 -83 no -- -- -- 80 - -
0ab4:b10c:fdc1 Access 149 -91 no -- -- -- 80 - -
3485:84b0:a824 Access CDE-GUEST 48 -82 yes 3 0 0 20 - -
2880:a296:53f0 Access Verizon-M2100-53F0 44 -91 no -- -- -- 80 - -
9058:513a:e7bc Access Zarandzoro 157 -91 no -- -- -- 80 - -
9058:513a:e7c2 Access 157 -92 no -- -- -- 80 - -
9058:513a:e7bf Access 157 -92 no -- -- -- 80 - -
ba98:13cf:8248 Access 157 -91 no -- -- -- 80 - -
9058:513a:e7c1 Access 157 -92 no -- -- -- 80 - -