Seamless Wifi - Multiple Access Points

Installing and Using OpenWrt Network and Wireless Configuration
1

Hi,

I am trying to set up a home network with multiple access points with the same SSID, Security and Password so that I can reach all areas of the house. I have an WRT1900ACS as the MAIN Access Point and hosting the DHCP server.

I want the other SLAVE Access Points (also WRT1900ACS) to use the DHCP Server on the MAIN Access Point and not serve out their own IP Addresses. I have connected the SLAVE Access Points to the Main Access Point via Ethernet into their Internet Port.

I tried setting the IP Address of the Slave router to the same subnet and turning off the DHCP server hopping that the client would see the DHCP server on the MAIN Access Point but that did not work.

I am using LUCI to configure the Access Points.

Can anyone point me in the right direction.

Thanks

Russ

2

If by 'Internet port' you mean the WAN port, you're doing it wrong :wink:

Anything on your LAN should only connect to your router's LAN ports - be it an access point, or a regular client.

You can (and should) assign fixed IPs to your access point; however, make sure they are outside the router's DHCP range. It's recommended to disable not only dnsmasq, but also odhcpd on the access points; you can also disable the firewall on them as well. Last but not least: make all your wireless access points broadcast on a different channel, so they don't interfere. If there's overlap in range, you might also want to adjust transmit power to ensure a smoother handoff (although that's not the only factor at play; but it will certainly help).

Good luck!

P.S. I've taken the liberty to correct the typo in your topic title.

3

Thanks for the spelling lesson - much apprecaitteddd!

All working now thanks to the simple cable move out of the WAN port. No more multiple SSIDs and the roaming works really well.

I did as you recommended and selected different channels - have not played with the power transmission yet. If it works don't touch.

I have not yet touched the odhcpd, dnsmasq and firewall - seems to work with these still enabled with the basic configuration applied. What is the consequences of disabling these services in the initscripts section?

Thanks again for your help - much appreciated

4

You'll disable DHCP v4 and v6, DNS, and the firewall. DHCP and DNS you should disable, so clients don't get confused when looking for DHCP or DNS servers. Disabling the firewall is optional, but you don't need it anymore since the devices are only passing LAN traffic anyway.

5

https://www.usenix.org/publications/login/april-2013-volume-38-number-2/wireless-means-radio

https://www.usenix.org/conference/lisa12/technical-sessions/presentation/lang_david_wireless

short version, put the APs on the same SSID/password and make sure they are
bridged, not routed from wireless to wired.

David Lang
k

1 Like
6

I wrote some step by step commands about Dumb AP (is what you describe) as well as Wireless Links using WDS or RelayD+IGMPProxy

It is not Luci but it is really easy to do connected to SSH (then you can see the changes in Luci)

In the WDS gist you will see how to setup add for your Dumb AP the wireless interface settings too.

If you want a proper working for all devices roaming network you will need to set, on same frequency (2.4ghz OR 5ghz), same channel (for example channel 6) EDIT, DONT USE SAME CHANNEL USE DIFFERENT FOR EACH AP, the same Network Name (ssid), the same encryption (WPA or WPA2), same key (wireless password) is the only way to have a flawlessly roaming for all devices. If you have a lot of interferencies or you dont want to deal with reduce a little bit the radio txpower then you could use different channels, but probably will get without connnection for a few seconds when you move from one place to another until the device recognice the loss of singlal strength and perform an scan on other channel to search for networks. At least you will not have to re-enter password. In some devices like very old notebook I even had to disconnect (disable wifi) and reconnect because when disconnect from network and reconnect does not scan other channels and keep trying to reconnect to same one.
If you have dual-band (2.4ghz and 5ghz) use different SSID's on each band or you will have problems with some devices, even modern ones. EDIT DONT NEED TO USE DIFFERENT SSID ON EACH BAND, READ BELOW NOTES

How to setup a Dumb AP, Wired backbone for OpenWRT / LEDE:

How to setup Wireless Links to avoid Wired backbone using WDS on Atheros for OpenWRT / LEDE

How to setup Client Bridged / Client Mode / RelayD and IGMPProxy for OpenWRT / LEDE

7

You shouldn't need to use the same channel on all APs.

I've deployed over 100 APs to cover a conference and just done same SSID, wifi
bridged to wired vlan (with dhcp on a server, not on each AP)

I did separate SSIDs for 2.4 and 5, but that was to encourage people to use 5
due to congestion, not because devices couldn't handle it.

I have an article at
https://www.usenix.org/publications/login/april-2013-volume-38-number-2/wireless-means-radio
and a video of a presentation at
https://www.usenix.org/conference/lisa12/technical-sessions/presentation/lang_david_wireless

These show what I did for the 2012 Scale conference, but I did the same thing in
later conferences (I ended up roughly doubling the AP density from what's shown
in the article)

David Lang

8

You are absolutely right, it is good for a conference... but when you work on a big building you will have constantly users that says "I lost connection" when moving to somewhere else and that is because some devices does not know that when signal is out must re-scan other channels and pay attention to same id, just update the list and show others and keep showing as connected the previous AP with low signal.. trust me, happened with at least 5 completeley different devices, atheros, intel, broadcom, all lastest Windows and driver. other devices works just fine, and happened the same on some cheap samsung phones too.

About separate SSID, happened to me too have devices, even with latest MacBook Pro (supposed to be state-of-the-art wifi) to keep trying to use same band instead of the other, and has no way to chose which one neither, and not so intelligent to detect when is needed to chose one or another depending on congestion...

When deploying AP for companies you need to have in mind that you will have a balance between old laptops 2.4, new laptops 5ghz capable, and a lot of BYOD devices of all kind and the ONLY thing that you need to achieve is get secure, get it working, get it easier to understand and use for users and reduce possible problems to minimum... :wink:

Thats because I do all this in that way... works for me! :slight_smile:

Thanks any way for your knowledge, it was very good to know about your big 100 AP and how was done, in my entire life I didn't count that much AP's yet... :blush:

ps: DHCP it is always on the MainRouter on the included links as you said.

9

You are absolutely right, it is good for a conference... but when you work on
a big building you will have constantly users that says "I lost connection"
when moving to somewhere else and that is because some devices does not know
that when signal is out must re-scan other channels and pay attention to same
id, just update the list and show others and keep showing as connected the
previous AP with low signal.. trust me, happened with at least 5 completeley
different devices, atheros, intel, broadcom, all lastest Windows and driver.
other devices works just fine, and happened the same on some cheap samsung
phones too.

well, when the conference covers around 100,000 sq ft of buildings, it's big
enough to run into any problem.

If you try to run everything on one channel, it just is not going to work.

About separate SSID, happened to me too have devices, even with latest MacBook
Pro (supposed to be state-of-the-art wifi) to keep trying to use same band
instead of the other, and has no way to chose which one neither, and not so
intelligent to detect when is needed to chose one or another depending on
congestion...

the devices have no idea of what congestion is, they connect to the strongest
signal that they have, and frequently manage the two bands separately, so they
would not jump from one band to another easily. In any case, you need to have
complete coverage of the facility with each band. The 2.4GHz band just doesn't
have enough channels to do this effectively, so you really want to have anyone
who can use the 5 GHz band.

proprietary, controller based systems do this by having the controller detect
that they device showed up on the 5GHz band and then ignore any requests it
makes to the 2.4GHz band. This is rather inefficient, and using appropriate
social engineering when naming the SSIDs solves this problem nicely (scale for
5GHz vs scale-slow for 2.4GHz for example)

When deploying AP for companies you need to have in mind that you will have a
balance between old laptops 2.4, new laptops 5ghz capable, and a lot of BYOD
devices of all kind and the ONLY thing that you need to achieve is get secure,
get it working, get it easier to understand and use for users and reduce
possible problems to minimum... :wink:

actually, I'd argue that in a business environment, you have a lot more control
over the devices than at a hobbiest conference (I was still running into 802.11b
only devices in 2014 for example)

Thats because I do all this in that way... works for me! :slight_smile:

You are very close to correct, but if you try to use a single channel for
everything, the entire network is going to collapse at very low traffic levels.

That's the reason I spoke up

One other thing I didn't mention in the prior e-mail, turn the power level on
the APs down as far as you can to get coverage of the area to minimize
interference between devices using different APs on the same channel, you want
to minimize the footprint of each AP so that there is as little interference
between APs on the same channel as possible.

David Lang

2 Likes
10

Thanks, I agree. I added some edits in previous post about the different channel use and different SSID on each band according.

11

Hey there.

Here's the code I use for provisioning my APs.
I use a couple of TP-Link 4900, one 4300 and one 1043, as a total of 5 devices at home, all in "dumb AP" setting.

As you can see, I didn't set up the wifi interfaces at all.
I just rely on all APs have proper vlans in place.

Since I use those dumb APs not only for APing but for providing individual vlan outlets, I just cannot provision the switch config in a generic way. All device are completely different.

At the bottom of the script, there's a block "some tweaking". It sets things that I think can do good for the connection in general, and additionally, it sets the "distance" parameter and the "beacon_int" parameter depending on the channel number. So 2.4GHz channels get "distance=20; beacon_int=300" and 5GHz channels get "beacon_int=100". That helps pushing clients to 5GHz.

I have a central box for DHCP, DNS and routing. I use that one (it's not an AP at all but a BananaPi M1 without wifi) to distribute my wifi settings to my APs.
I just call ssh ap1 ash < provision-wifi.sh

Just as dlang mentioned, I'd not use the same channel on all APs. You just clutter the capacity and leaving other capacity unused. Use different channels per AP, and if you need to have overlapping channels, try to assign them to APs as far apart as possible.
As you see my script, the 2.4GHz channel number 5 is assigned twice, but AP2 and AP3 are on the opposite corners of my house, one in the basement ant the other in the 2nd floor.

I tried much with channels and found out:

  • There's very little chance for one client to switch from one AP to another if the current AP is strong enough. Making it less strong by reducing the APs power is the best thing you can do.
  • There's a threshold configuration in the client driver, but that's a thing you can barely influence.
  • If a client decides to switch AP because of poor connectivity, the client usually performs a full scan. So there's no need to keep channels close or even overlap. Use none overlapping channels.

Regards,
Stephan.

2 Likes
12

I added some edits in previous post about the different channel use and different SSID on each band according.

Yes, I know this... maybe I just explained my setup badly, in some places I have some old laptops (from 2010-2013) with shitty wifis not smart enough to to that, all other devices works just fine, but 3 or 4 devices that fails of 40 total are just enough to get people angry when lost connectivity when moving from one room to another...
I set up AP for just one room, or in some cases two... when more than 1 wall is the equation there is signal and network visible but just crappy speed, unreliable, so it works better with just the needed signal power and add more APs somewhere else to cover the other areas.

13

Thanks for sharing your gist, it is really interesting way to setup many AP's.!

14

great info here, thanks!

15

hi @golialive are you still using same setup for pushing clients more to 5Ghz band? Have you found a better way or this one still works ?

17

Hey there.

Yes, the setup is still the same. I changed the values of beacon_int from 300/100 to 500/100 to make it a little more likely for devices to see the 5GHz APs, but the actual mechanism is still the one onf my gist.

Regards,
Stephan.

1 Like
18

I just tested successfully yesterday configuration for ieee80211r Fast Transition WiFi Roaming.
Is somehow related to this...

19

Yes, 802.11r, if properly configured and the clients support and use it, can speed the "handoff" from AP to AP. At my location, only iOS devices seem to use it. The transition time drops from around 1.5 seconds to a small fraction of a second. We find it only noticeable when using FaceTime in that there isn't the obvious, momentary freeze in video and audio that there was previously.