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New Contributor
Posts: 3
Registered: ‎03-27-2012

802.11n AP connected to a switch that only supports 100 MB

I am troubleshooting a customer network that has deployed AP125s with HP ProCurve switches. The switch ports only support 100 Mb.  In this scenario should HT be turned off to accomodate the 100 Mb switch port?

Guru Elite
Posts: 20,773
Registered: ‎03-29-2007

Re: 802.11n AP connected to a switch that only supports 100 MB

No.  It should be just fine.  Make sure the switch is on auto/auto and you adhere to the 3/4/5 rule.



Colin Joseph
Aruba Customer Engineering

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New Contributor
Posts: 3
Registered: ‎03-27-2012

Re: 802.11n AP connected to a switch that only supports 100 MB

What is the 3/4/5 rule?  And how does it apply to this scenario.

 

Thanks.

Guru Elite
Posts: 20,773
Registered: ‎03-29-2007

Re: 802.11n AP connected to a switch that only supports 100 MB

I apologize.  Just make sure that the ethernet cable is no longer than 100 meters long, so that the AP will power up properly.

 

 



Colin Joseph
Aruba Customer Engineering

Looking for an Answer? Search the Community Knowledge Base Here: Community Knowledge Base

New Contributor
Posts: 3
Registered: ‎03-27-2012

Re: 802.11n AP connected to a switch that only supports 100 MB

Thanks.

Aruba Employee
Posts: 3
Registered: ‎04-02-2007

Re: 802.11n AP connected to a switch that only supports 100 MB

You want to leave HT enabled even if the AP's ethernet port is only at 100 Mbps because we want to operate the link from the wireless client to the controller/network at the highest rate possible. Disabling HT will cause the wireless link to operate at a peak of no more than 30 Mbps (at 54 Mbps PHY rate). Enabling HT on the other hand could potentially tilt the balance the other way so that the wired link could be slower but it isnt half as bad as it sounds.

 

It is also important to recall that the numbers associated with 802.11 rates are the sum of both directions (uplink + downlink) because the 802.11 links are half-duplex. Your Ethernet link is probably 100/full-duplex. You can easily construct test cases where the numnerical difference will show up, but for much of the time with real users/traffic, it will be harder to detect that the Ethernet link is operating slower than the wireless link.

 

Your users will be happier with HT enabled than otherwise. 

Tom
Occasional Contributor II
Posts: 12
Registered: ‎11-06-2011

Re: 802.11n AP connected to a switch that only supports 100 MB

Interesting replies to the HT and 100Mbps switch. Users who are hard wired and wireless (Laptops) will run into issues with HT enabled, as Windows metrics will prefer the wireless connection as it reports a connection over 100Mbps. I have a number of sites with only 100Mbps, even down to the controller :( and I'm forced to disable HT due to performance issues, otherwise I need to set the metrics manually on each machine to force it to use Ethernet rather than wireless. At Airheads LV I did raise this issue and was told it was ok to disable HT, otherwise set the metrics under Windows. To tell you the truth, even at 54Mbps on my desktop, I can't tell the difference between wired and wireless, but end users like to complain about it.
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