HT-protection=Green field;

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reviewing my radios in the AP 330

and I see that both the 2.4Ghz and 5Ghz have HT-protection set to Green field.
I have scoured the radio profiles and don't see any option to change or set the HT-Protection mode.

Is this set because I selected to disable b clients?

my understanding is that 802.11a/b/g devices won't be able to communicate with an AP in green field mode.

I did not select to disable a/b/g clients, and I thought the mode would have been mixed mode.
Wifi0
Channel width=20Mhz; HT-protection=Green field; Deny client=11b;
Wifi1
Channel width=40Mhz; HT-protection=Green field; Deny client=11b;



Will the AP switch over automagically if it hears an a or g client to mixed mode?
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Andrew MacTaggart, Champ

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Posted 5 years ago

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Crowdie, Champ

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Have you looked at your access point's configuration? I always disable 802.11b clients but I cannot see anything in my access point's configuration that mentions protection, greenfield or HT.

Be very careful with the term "Greenfield" as some vendors use it to describe an installation where no previous equipment exists and some vendors use it to describe a 802.11n or 802.11ac deployment with no 802.11a/b/g compatibility.

I had this discussion with Cisco a year or two ago as Cisco does not support a greenfield mode with no 802.11a/b/g compatibility. The reason for this is that all 802.11 networks have a requirement to be able to co-exist with other 802.11 networks and if the 802.11a/b/g compatibility was disabled the normal medium access methods (Duration/ID field and NAV) would not work as the 802.11n/802.11ac access point would not be able to detect/decode the 802.11a/b/g frames.
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Hi Crowdie

I hear you about the term "Green Field", but that is the term used in the 330 AP and the CWNP official study guides, but we could just call it HT-protection mode 0.

When I saw it via the command line, show interface wifi1 and show interface wifi0, I was curious to figure out how it was set.

Reading Devin's blog
http://www.cwnp.com/cwnp_wifi_blog/80...

states that if the AP detects a/b/g clients that the mode will change.

"From lab work, I’ve found that you can basically call mode 0 “pure mode” just like we used to have with just 802.11g. If the 802.11n AP hears nearby APs and STAs that are non-HT capable, then it flips over to mode 1. If a non-HT station associates to an 802.11n (HT) AP, it flips over to mode 3."

I just wanted some clarification on this value, since I did not set it on purpose.

I need to check a few APs where I know I have older devices that don't support HT and see if the protection mode is different.
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Confirmed

APs switch protection mode when it detects non HT devices

we have an area where we have older IPOD Touches hanging out and they only support b/g

show interface wifi0 from an AP with b/g clients floating about

Channel width=20Mhz; HT-protection=Legacy protect; Deny client=11b;

Wifi1 - With IPADv2 in the area

Channel width=40Mhz; HT-protection=Channel protect; Deny client=11b;

Mode 0 would be Greenfield (No Protection) Mode = Aerohive mode Green Field

Mode 1 would be HT Nonmember Protection Mode = Aerohive mode ???????
Have not seen this one yet, would require hearing non HT non member

Mode 2 would be HT 20 MHz Protection Mode = Aerohive mode Channel protect
All clients are HT but a HT STA joins that only supports 20Mhz channels
Which makes sense since I have IPADv2 that only support 20Mhz channels

Mode 3 would be HT Mixed Mode = Aerohive mode Legacy protect
a/b/g client joins the BSS, such as IPODv2
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From the Aerohive 802.11n Primer whitepaper:



Page 8 - Compatibility modes of .11n
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Legacy protect sounds different then Legacy mode
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For more info have a look at http://www.cwnp.com/wp-content/upload...

An old document but certainly a goodie....

Also have a look at the "802.11n interoperability and coexistance" section on page 10 of http://airmagnet.flukenetworks.com/as...

The big question is how do we match the modes to the wifi values?
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I think I am just missing mode 1 naming convention, because I have not seen it yet in the wild, but it would be good to confirm the naming with the mode.

Did you get your switch design guides yet. I only have the switch training materials,but I am not sure if it would be helpful or if Aerohive would let me share it with you. If they approve I can send it your way.

but I can tell you that STP is disabled by default.
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How good is the switch training materials? If it is good I'll get a copy from Aerohive.
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it's 600 pages of how to configure the switches
dot1q
link aggregation
STP
port configuration
etc

also covers routers and CVG

I didn't take the course, but David included it.
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That sounds extremely useful. What is the training called?
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i have rev8a, which is about 5 months old, they have released other switches since then, so there might be a newer version.
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I obtained the training notes from Aerohive and had a really good look. The switches look very good but the devil is always in the small print. We need a cloud managed solution and HMOL managing access points and switches looks pretty impressive.

I looked at a number of my sites and the wifi0 interfaces were always either Greenfield or Legacy Protected. I looked over several dozen access points at various sites and only had the two interface statuses.
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I think you will find Channel Protect when using Ipad version 2 since it is HT but only supports 20Mhz channel on wifi1 or some similar HT device that only support 20Mhz channel.

for wifi0 you would have to be using 40Mhz channel and have an HT device that only support 20Mhz channel, But I don't think anyone would do such a thing.

for example comparing Ipad mini - they make a point to include 40Mhz support

2.4 GHz, 5 GHz - Concurrent
Tx 1 tested Spatial Streams 2.4 GHz
Rx 1 tested Spatial Streams 2.4 GHz
Tx 1 tested Spatial Streams 5 GHz
Rx 1 tested Spatial Streams 5 GHz
Short Guard Interval
TX A-MPDU
40 MHz operation in 5 GHz

vs

an Ipad 2

2.4 GHz, 5 GHz - Switchable
Tx 1 tested Spatial Streams 2.4 GHz
Rx 1 tested Spatial Streams 2.4 GHz
Tx 1 tested Spatial Streams 5 GHz
Rx 1 tested Spatial Streams 5 GHz

So in this case we have a HT device that only supports 20Mhz channel

thus the Channel Protect
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I did some testing and I found the following:

* When my 802.11n adapter connected in 802.11n mode the HT-protection is Greenfield (no surprise here)

* When my 802.11n adapter connected in 802.11g mode the HT-protection is Channel Protect (no surprise here either)

* When my 802.11n adapter connected to the 5 GHz 40 MHz channel in Fat Channel Intolerant mode the HT-protection is Greenfield

I could not produce a third HT-protection mode.
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"When my 802.11n adapter connected to the 5 GHz 40 MHz channel in Fat Channel Intolerant mode the HT-protection is Greenfield "

My understanding is that HT intolerant mode applies only to 2.4Ghz. and that 5Ghz will always set the 40 Mhz intolerant sub-field to 0 thus allowing 20/40 Mhz BSS's