topic Re: Weak Signal Probe Request Suppression does not work? in Aerohive Migrated Content

Weak Signal Probe Request Suppression does not work?

andreas_brueck — Tue, 11 Feb 2020 20:54:42 GMT

Hello everybody,

we have some trouble with sticky clients which does not roam to a better access point. Because of that i activated the option Weak Signal Probe Request Suppression for my 2,4 and 5 Ghz radio profiles.

After that i did a complete configuration update on all access points. Two days later i checked the connected clients for some access points and i found clients with really poor SNR values.

How is it possible? Is it correct that clients with a poor SNR still will be connected to an not optimal access point? Maybe i don't understand this option correctly.

We are using the on-premises Hivemanager NG (build version 19.5.1.7-NGVA ) and a lot of AP230 (HiveOS 10.0r5 build-228634 ).

Thank you in advance.

Regards,

Andreas Brück

Re: Weak Signal Probe Request Suppression does not work?

bpowers — Tue, 11 Feb 2020 21:40:23 GMT

Andreas,

That feature only works for the initial association/authentication attempt or when a device chooses to roam.

A probe request is intended to do a couple things. Mainly gather a list of neighbor APs for when a device chooses to roam. They are also used to gather a list of APs to associate too.

So once a client is associated to the WLAN if it moves away from it's associated AP, and chooses not to roam, this feature will not help. But once it does choose to roam, this feature will limit the number of APs that will send a Probe Response after the station sends out the Probe Requests.

If you're looking to help users roam to different APs, you might benefit from altering the mandatory and optional data rates for the 2.4/5 GHz bands for the SSID(s) you use. As if they are default, then the client devices can stay associated to an AP so long as it's frames can be decoded at 1 Mbps on 2.4 GHz and 6 Mbps on 5 GHz. The below image depicts this somewhat. In this regard, you must have at least one data rate set as Mandatory. This is the minimum needed to stay connected to an AP. Some folks like using 12 Mbps. I've seen sites where all rates are disabled below 24 Mbps. YMMV and if it were me, I'd make incremental adjustments to this to better understand how your client devices act with such a change. I also wouldn't use any rates other than 6, 12 or 24 as the mandatory rate even though you can as those are the 3 rates per the 802.11 standard that should be mandatory rates.

Re: Weak Signal Probe Request Suppression does not work?

samantha_lynn — Tue, 11 Feb 2020 22:02:30 GMT

The weak SNR probe suppression should be dropping the weaker signals, you might want to open a case so we can investigate that further, but for clients that aren't connecting to the best AP I would recommend adjusting lower data rates rather than the weak SNR probe response setting.

If you disable the lower data rates on your SSIDs, this will require a stronger connection between the AP and the client device. That will mean that the client device needs to be closer to the AP before connecting/roaming. Not only will this reduce the chances of unintentional roaming, but it will also reduce the distance the packets need to travel, which will also reduce collision and interference on your network.

To disable the lower data rates we need to go to Configure> Network Policies> Select the network policy> Open the SSID> Expand Additional Settings> Customize Optional Settings (at the end of the page)>In the 2.4 GHz 11/bg Rate Setting section, we want to turn 1Mbps-9Mbps to N/A. In the 5.0 GHz 11a Rate Setting section we want to turn 6 Mbps and 9 Mbps to N/A. You'll need to update the APs again to use these new settings, but a delta update should be fine for these changes so you don't need to reboot your AP.

Re: Weak Signal Probe Request Suppression does not work?

andreas_brueck — Wed, 12 Feb 2020 20:04:50 GMT

Hello Brian, hello Sam,

thanks for your explanation and your suggestions. I already configured the data rates to 12 mbit/s for all SSIDs before i activated the SNR probe suppression, but just for 802.11 b/g and a.

What is about the 802.11n standard? Make it sense to deactivate some MCS rate Settings?

I found also a option under "Monitor --> Devices --> Choose an access point --> Edit --> Additional Device Settings --> Neighboring Devices --> Roaming Threshold" which is set to High. Is it necessary to set this threshold to Medium or Low?

Re: Weak Signal Probe Request Suppression does not work?

andreas_brueck — Wed, 12 Feb 2020 20:24:50 GMT

I have an additional question:

Is it necessary to set the data rate 24 Mbps to Basic instead of Optional ? So that 12 and 24 Mbps are both set to Basic for 802.11a/b/g or makes it no difference?

Re: Weak Signal Probe Request Suppression does not work?

bpowers — Wed, 12 Feb 2020 20:44:16 GMT

As a rule of thumb, most people say to not adjust any of the MCS rates. With your current settings, you're still seeing clients with weak RSSI? If so, what type of power settings are configured for your radio profiles? Is it perhaps, the output power of your APs far exceeds the output power of your devices? In this scenario, the client device may see the AP strong, but the AP cannot hear the client well. This could be causing the client devices to hang onto APs longer than necessary.

Re: Weak Signal Probe Request Suppression does not work?

bpowers — Wed, 12 Feb 2020 20:47:12 GMT

Beacon frames by default come out at the lowest configured "Basic" rate. So having 12 and 24 configured as basic would have little impact on this. There is however a setting in the radio profile under High Density WLAN Settings called "Enable settings designed to optimize performance in a high-density WLAN" that then gives you a dropdown selection to change the data rate that the Management Frames are transmitted at. The settings are Low and High. This is basically changing it from the lowest configured Basic rate to the Highest configured Basic rate. The combination of the two could have some impact. But getting that high of a basic data rate could have other implications that outweigh the possibility of it forcing clients to roam.

Re: Weak Signal Probe Request Suppression does not work?

andreas_brueck — Wed, 12 Feb 2020 21:08:37 GMT

Thanks, that is nice to know. Yes, we still have some clients with poor RSSI and SNR values. But i think its less than yesterday, i need to observe this the next days. The Maximum Transmit Power is set to 20 dBm for the 5 ghz band and 17 for the 2,4 ghz band. Are this values to high?

Re: Weak Signal Probe Request Suppression does not work?

andreas_brueck — Wed, 12 Feb 2020 21:10:27 GMT

Ok, thank you Brian. That is very useful to know. So i will still use the configuration as shown in the pictures.

Re: Weak Signal Probe Request Suppression does not work?

bpowers — Wed, 12 Feb 2020 21:40:46 GMT

While those are about as high as they can be set, what are the APs actually running at? You can add a column to your UI view to show their channels and the currently set power. Decreasing power is probably the simplest way to force clients to roam as if they cant hear the AP they're connected to in a given area, they'll surely roam to a stronger AP.

Re: Weak Signal Probe Request Suppression does not work?

andreas_brueck — Wed, 12 Feb 2020 22:20:14 GMT

The most of the use the maximum of 20 dBm. Ok, i think i will try to reduce the transmit power by 1 dBm step by step. But i hope that the coverage is high enough at our campus. Thank you very much for your help.

Brian, what do you know about the option "roaming threshold" in the fourth picture?

Re: Weak Signal Probe Request Suppression does not work?

bpowers — Wed, 12 Feb 2020 22:32:51 GMT

The below is from the help file. To me this is a configurable parameter when Layer 3 roaming comes into play. To optimize and/or speed up roaming of Layer 3 (IP) boundaries. And not necessarily relevant to your current issue.

From the help file:

In the Roaming Configuration section, you can define the hive members to which you want other hive members to send Layer 3 roaming-related information (Included Neighbors) and those to which you do not want APs to send such information (Excluded Neighbors). Note that included and excluded neighboring hive members must have static IP addresses for this feature to work properly.

Roaming Threshold

Set the volume of traffic that the selected neighbors will accept through GRE (Generic Routing Encapsulation) tunnels to support Layer 3 roaming. This option gives hive members the ability to push tunnels to other members for better tunnel load balancing. For example, if one AP near an entrance gets overloaded with tunnels, you can lower its threshold to medium or low so that more tunnels terminate on other APs.

This setting only takes effect when the APs function as portals and Layer 3 roaming is enabled.

From the Tunnel Threshold drop-down list, choose a level determining the amount of traffic that the selected APs will accept through GRE tunnels. To accept a relatively low number of tunnels, choose Low. To accept a relatively moderate number of tunnels, choose Medium. To accept a relatively high number of tunnels, choose High. The default setting is High.

Included Neighbors

Because basic hive communications occur within a Layer 2 broadcast domain, to span subnets, at least one hivemember in each subnet must be able to detect another member in the other subnet. If hive members in different subnets are within radio range from each other, they can discover each other automatically. If hive members in different subnets are out of radio range from each other, you can define them as neighbors to each other. A hivemember defined as a neighbor exchanges roaming cache information with all hive members outside its subnet. Wireless clients can then roam between the defined neighbor and any hive member in the other subnet.

APs that you want to include or exclude as neighbors for Layer 3 roaming must have static IP addresses.

To add an AP in the list of included neighbors, select the AP name in the Available Neighbors column, and then click the right arrow ( > ) to move it to the Selected Neighbors column. Repeat this to add more neighbors. You can add up to 32 neighbors.

To remove an AP name from the Included Neighbors list, select the AP name in the Selected Neighbors column, and then click the left arrow ( < ) to move it back to the Available Neighbors column.

You can select multiple APs by SHIFT-clicking to select multiple contiguous items and CTRL-clicking to select multiple noncontiguous items. You can also move all the APs from one column to the other by clicking >> and <<.

Excluded Neighbors

There might be a case where you do not want a hive member to exchange roaming cache information with other members in a different subnet. If so, add them to this list. Even if the excluded neighbor is within range of another hivemember in a different subnet, they will not exchange roaming caches.

To add an AP to the list of excluded neighbors or remove it from the list, follow the same procedure explained above for adding and removing included neighbors.

Re: Weak Signal Probe Request Suppression does not work?

andreas_brueck — Wed, 12 Feb 2020 23:01:30 GMT

Shame on me, normaly i take a look on the help page before i ask any questions. Thank you very much for your help.