Migrating to 1250's

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Jul 21st, 2008
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We are thinking of migrating to 1250's to start preparing for 802.11n.

My questions are can you have a mixed environment with 1130's, 1231's, 1242's and 1250's. If so, are there any problems with roaming between different AP's? or Power requirements We have for the most part WS-C3750-48PS-S, WS-C3750G-48PS-S and 6500's

WS-X6148A-GE-45AF cards in the access closets.

Right now we have Cisco 7921 phones and Vocera badges on "B/G", wireless laptop carts on "A".

I am not concerned to much with increasing speed at this point I am more concerned with having a stable environment until we complete the migration.

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Leo Laohoo Mon, 07/21/2008 - 19:51
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The Cisco Aironet 1250 AP's, with both radio modules installed, requires a minimum of 18500 milli-watts of power. PoE switches can only go as far as 15400 milli-watt.

Cisco WS-C3560E-XXPDX-F and WS-C3750E-XXPDX-F (with version 12.2(44) IOS) will work (power inline port max nnnnn in interface configuration mode).

If you don't want to have additional financial outlay for extra switches, then use only one radio module.

ahkal_cisco Tue, 07/22/2008 - 03:59
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You can also use the power injector, this will feed 56 volts to the AP over the ethernet

ppellettiere Tue, 07/22/2008 - 05:37
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I am not sure I know what a power injector is

is it a software upgrade or a physical piece of hardware.

ppellettiere Tue, 07/22/2008 - 05:36
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If we only use 1 radio module would I be able to support B/G/A until we upgrade to the newer switches.

ericgarnel Tue, 07/22/2008 - 05:49
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No, the modules are either 2.4 and 5GHz. So you would have to decide between b/g or a. Keep in mind that Cisco discourages the use of 802.11n on the b/g side and makes it very difficult to enable on the b/g side.

As stated, you would need the 1252 power injectors or power supplies to power both radios. The power injectors can live in the wiring closet near the current switches and provide PoE to the APs.

We have 90+ 1252s running this way just fine, with the rest coming straight off the 3560-E switches.

Rob Huffman Tue, 07/22/2008 - 05:50
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Hi Peter,

The single Radio Module will not support b/g/a as b/g are supported on the 2.4GHz Module and "a" is on the 5GHz module.

As for the Power Injector, it is a Hardware device. This is the one for the 1250, AIR-PWRINJ4=Power Injector - 1250 Series

Cisco Aironet 1250 Series Ordering Guide


Hope this helps!


mthurman Thu, 07/24/2008 - 11:30
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A Cisco Wireless SE told me that with the next version of WLC software we would be able to support 1252 AP's with 15 Mw and run both radios. Was he right?

ericgarnel Fri, 07/25/2008 - 05:22
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That is the 1st time I have heard that.

I would guess that the power hardware on the 1250s would need to be able to accept the lower wattage and power both radios at the same time.

Also, I'm not sure what role the WLC has in actual PoE management, as it usually is controlled by the power subsystem in IOS. I had to upgrade my 3560-Es to 12.2.44 (SE-1) to make use of the enhanced PoE. Also, the 3560-E series have a larger power supply than the standard 3560s and are swappable.

That would be great if that is the case. Did he mention what the rev of code was? The latest is 5.151.0

mthurman Fri, 07/25/2008 - 06:29
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I was trying to read through the release notes for 5.151.0 and I did see something about being able to configure the 1252 with a command for pre-standard PoE so they would work with 15.4 Mw, but not sure if I was reading it right.

ericgarnel Fri, 07/25/2008 - 06:44
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from http://www.cisco.com/en/US/docs/wireless/controller/release/notes/crn511510.html#wp234040

"Configuring an Access Point's Prestandard Power Setting

An access point can be powered by a Cisco prestandard 15-watt switch with Power over Ethernet (PoE) by entering this command:

config ap power pre-standard {enable | disable} {all | Cisco_AP}

A Cisco prestandard 15-watt switch does not support intelligent power management (IPM) but does have sufficient power for a standard access point. The following Cisco prestandard 15-watt switches are available:


•WS-C3550, WS-C3560, WS-C3750


•2600, 2610, 2611, 2621, 2650, 2651

•2610XM, 2611XM, 2621XM, 2650XM, 2651XM, 2691

•2811, 2821, 2851

•3631-telco, 3620, 3640, 3660

•3725, 3745

•3825, 3845

The enable version of this command is required for full functionality when the access point is powered by a Cisco prestandard 15-watt switch. It is safe to use if the access point is powered by either an IPM switch or a power injector or if the access point is not using one of the 15-watt switches listed above.

You might need this command if your radio operational status is "Down" when you expect it to be "Up." Enter the show msglog command to look for this error message, which indicates a PoE problem: "

Also from the same url:

Enhanced PoE switches-Enhanced PoE switches (such as the Cisco Catalyst 3750-E Series Switches) can be used with 1250 series access points to auto-negotiate a power level in excess of 15.4 W per port.

It is my understanding (correct me if I am wrong on this) that the switch power subsystem/supply can only dole out so much power either per port or overall regardless what the controller indicates.

Cisco power calc tool: http://tools.cisco.com/cpc/

(requires login)

dennischolmes Fri, 07/25/2008 - 11:39
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Both modules will be supported at 802.3af power standards but you will be giving up some features like spatial radio streams. Also, bear in mind that the 1250 signals differently for power and may require a dongle to work with any pre standard 802.3at devices you might purchase.

Anonymous (not verified) Thu, 10/16/2008 - 09:07
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rochoa8aeg Mon, 08/25/2008 - 14:33
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My understanding on the PoE process on the 1242, 1131, or anything pre-1250 AP is that since the ethernet port is 10/100 a regular Cat5e cable will use 2 pairs for data and the remaining 2 pairs for power.

On the 1250 APs the ethernet port is a Gig Port... So if a Gig Port uses all 4 pairs for data, how does it PoE provide power to the AP?

Scott Fella Mon, 08/25/2008 - 17:12
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mark.cronin Wed, 01/28/2009 - 07:16
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Adding to this post


1) To provide 802.11b/g data coverage for clients

2) To identify rogue access points internal to the building using the location tracking appliance. The rogue access points can be

802.11b 2.4Ghz

802.11g 2.4Ghz

802.11a 5Ghz

802.11n 2.4Ghz

802.11n 5Ghz

For requirement 1 , I would install the Cisco 1242 LAP

For requirement 2 , not sure , possible

Cisco 1250's with modular radios ???

Has anybody got any views on this?


Leo Laohoo Wed, 01/28/2009 - 16:10
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If you want to identify the location of the Rogue AP, just do simple triangulation with a minimum of two to three LAP (joined to a WLC). I've done this several times. Whether or not you need the 1140/1250 to locate Rogue 802.11n, on the other hand, is something else.

Get a packet sniffer (like Netstumbler) is a start.

mark.cronin Thu, 01/29/2009 - 06:50
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We have tools like netstumbler, the problem with them are that you need someone physically onsite to use them. I am just looking at the problem of how to identify all 802.11 wireless rogues. I am currently limited to only using the cisco 1242 for client data, it looks like I will need to install some 1140's or 1250's in monitor mode just so that I can detect 802.11n.


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