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Author Topic: How are SSIDs broadcast on WiFi?  (Read 293 times)

broadstairs

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How are SSIDs broadcast on WiFi?
« on: February 25, 2021, 05:22:04 PM »

Interesting topic came up on another forum talking about 2.4ghz only devices and suggesting you need to turn off 5ghz if the SSIDs are the same on both. Now I always assumed that the SSIDs were broadcast on their relative channels so a 2.4ghz only device could only see 2.4ghz SSIDs and vice versa. Is this true?

Stuart
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g3uiss

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Re: How are SSIDs broadcast on WiFi?
« Reply #1 on: February 25, 2021, 05:27:02 PM »

I use Unifi AP,s. The SSID is the same for both and the device will lock on to the best signal. As proliferation is better on 2.5gb there is a slight tendency to prefer that, however I got round that by reducing the power on 2.5 and increasing on 5gb. Not sure if that answers the question and might be device specific
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broadstairs

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Re: How are SSIDs broadcast on WiFi?
« Reply #2 on: February 25, 2021, 05:36:10 PM »

I am talking about devices which ONLY use 2.4ghz, will they see only 2.4ghz SSIDs. I believe that is true am I right?

STuart
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licquorice

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Re: How are SSIDs broadcast on WiFi?
« Reply #3 on: February 25, 2021, 05:47:19 PM »

A 2.4Ghz only device can obviously only 'see' the 2.4Ghz SSID, however, for some inexplicable reason although they don't have 5Ghz capability, some Smart devices appear not to like 2.4Ghz and 5Ghz signals having the same SSID. I really don't understand why that should be so. The only reason I can think of is that the router somehow initiates the connection at 2.4Ghz and then tries to force the device onto 5Ghz which it obviously can't 'see'.

Its a particular problem with the BT SH2 as the SSIDs can't be split.
« Last Edit: February 25, 2021, 05:49:44 PM by licquorice »
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meritez

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Re: How are SSIDs broadcast on WiFi?
« Reply #4 on: February 25, 2021, 06:29:55 PM »

From what I understand when a wireless client speaks to an access point, the access point asks the client what it supports.

The 2.4 only client states 802.11b, 802.11g and 802.11n.
The 5ghz only client states 802.11a, 802.11n and 802.11ac.

Some of these 2.4ghz devices seem to not know that 802.11n supports 5ghz.
So the client states I support 802.11n, and the access point tries to connect the client to 5ghz.

So I put it down to lazy programming in the client.
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Alex Atkin UK

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Re: How are SSIDs broadcast on WiFi?
« Reply #5 on: February 25, 2021, 08:26:47 PM »

I've never heard of this specifically but band steering has never really been recommended as its known to be pretty dumb about things and I guess this is what they meant.

I've always kept SSIDs independent because if you leave it up to the client they can pick 2.4Ghz for its stronger signal and AFAIK none of my APs ever had band steering until the nanoHD.
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Weaver

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Re: How are SSIDs broadcast on WiFi?
« Reply #6 on: March 12, 2021, 03:55:07 AM »

I have the same SSID set on 2.4 and 5GHz on my old 802.11n WAPs; no problem with any of the devices encountered.
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