I updated a customers caps from ros 6.39.1 to 6.40.3. Now I notice that both caps (a hAPac and a wAPac) have selected the same channel for both radios. I didn’t notice if they did so before the update. How can they do that for both radios? They are located just 10m from each other. I could understand this if they were located far apart. I could understand this if it was only the 2.4GHz radio (lots of neighbors). But how come they do this for both radios?
The hAPac runs capsman as well as being a caps.
Noone has experienced this?
This is the second time I have this issue. The first time I thought all the wAPac’s I had with me was from a defective batch, and replaced them with hAPac’s.
As far as I understand, Mikrotik chooses least busy wireless channel only on startup and after that never checks if it is the best (least busy). So, after CAPsMAN restart, if both APs are starting simultaneously, they can choose the same free channel. Starting from version 6.39 it is possible to tell CAPsMAN to periodically check for another free channels.
What’s new in 6.39 (2017-Apr-27 10:06):
*) capsman - added support for “background-scan” and channel “reselect-interval”;
Thanks. You may be onto something. Restarting the cap makes it select another 2GHz channel, but it keeps using the same 5GHz. There’s a lot of unused 5GHz channels in the building, and the the APs are within range of each other (-58dB). Is something wrong with the wAPac channel selection that makes it select the channel of the strongest neighboring AP? (A ‘<’ swapped with a ‘>’ or ‘max()’ swapped with a ‘min()’) or something like that in the code?
There is another bug in the wAPac: If country is set to Norway, and channels is set to auto, the 5GHz radio keeps selecting channels that is 5MHz less the actual channel frequency. I wouldn’t be surprised if there is another bug in the wAPac as well.
Now I’ve replicated this issue at home.
Took a brand new hAPac and a new wAPac, ros 6.40.3, copied system identity, capsman, caps, bridge, vlan, switch and IP settings from the customer. They are connected to each other with a 30cm cable, and they select same channel for both radios. I live at at place with no nearby wlans, except for my homewlan. Rebooting units just makes them pick the same channel again, even if I reboot the wAPac after the hAPac has finished booting.
I can confirm that this does happen, i had to manually set separate channels on my CAPs in order to avoid they interfere each other on same freqs.
Also this isnt best solution, as there are also very close surrounding networks and they also keep changing freqs and sometimes they again hit my frequencies which makes problems on network.
I’m currently trying to simplify config as much as possible to isolate the issue. This has revealed two other issues that I think are bugs. Those two are:
reset-configuration deletes all files on unit. This is causing problem when I want a script to run after reset - the script file is no longer there!
wlan interface controlled by caps are unable to use capsmanager running on the same unit, unless there is a vlan defined for discovery. That is - if vlan is defined on bridge, caps can connect using layer2 to capsman on same unit. If no vlan is defined layer2 will fail, but layer3 will connect - and disconnect within 10 seconds. In order to simplify configuration, my idea was to not use vlan. Turns out it can’t be made that simple.
I got to a very minimal config demonstrating the problem. I wrote down all the changes I did to the default config. Resat config, went through all the steps I had written down, and the problem was replicated. Then I connected another wAPac running ros 6.35 - which also got the same frequency. Then I connected another hAPac running ros 6.39.2 as cap, which also the same frequency. SO, I had 4 devices, all selecting the same frequency!
Then I got the idea to see if this also happens if I use the hAPac running ros 6.39 as capsman. I started out changing the cap setting on the hAPac running ros 6.40.3, just because I had that winbox window in front of the others, even though I had not configured capsman on the other hAPac yet. Then I, by accident, pressed the switch that disables the power outlet where they all were powered. When they got the power back, the problem was gone. All three remote caps selected different channels. Then I changed the local cap back to using the local capsman, and it also selected a different channel.
So, is the way to solve this issue to set the wlan running on same device as the capsman to use a capsman on a device not running capsman, and then change it back to the local capsman?
I had to test this. I logged onto my customers network. Changed the hAPac to use a not existing capsman. Then I restarted both access points. The wAPac started up fine, using another channel than before. Then I changed the local interface on the hAPac to use the capsman in same device, and it also worked - all though it did select the same channel as before. So this seems to be a workaround. Problem seems to be related to cap on same device as capsman connecting to capsman before other devices.
So, what happens if power goes down and devices restarts? I rebooted the devices at customer site - problem did not reappear. I rebooted my test devices at home - problem did not reappear here either.
Time will show if this process is a working workaround next time I run into this issue.
New customer - same problem. What appeared to solve the problem last time, does not work now.
This setup differs in the way that I put the wAPac as capsman, and hAPac as cap (last time it was the other way around). Both selects 5180MHz for 5GHz. For 2GHz the select different channels.
Apparently a few others have ran into this as well. What are you guys doing when you run into this?
Country tested with norway (frequency list know to be incorrect for wAPac models), france and UK. There are no other 5GHz networks in range at this customers site. The same goes at my house where I replicated the issue. For the two previous customers where I ran into this, there were some other 5ghz in range.
whats your channel configuration and routeros version?
i only have 2.4ghz implementation
i have configured channel this way and cAP are jumping between the 3 channels specified without issue selecting the channel with neighboring network with less signal level, routeros 6.40.5
I have a crowded environment with 40+ neighboring bssid’s on any ap, my own ap are not the strongest ones
in further testing i have found that when a Cap stays on “old” channel after a scan, never scan again, that is “reselect interval” setting does nothing after a scan without channel change.
i remove “reselect interval” setting and make a scheduler to make Cap reselect channel every interval i want
I ran into this issue again. What was the solution this time was to downgrade firmware, and upgrade firmware again. No config changed - problem gone.
I wonder if that’s going to be the solution next time as well.
I am also seeing this, after reboot both AP come up on same channel on 40MHz… unless i have screwed up the channel selection list - either way, hitting Reselect Channel it will then pick a separate channel.
