POE problem with 802.1a and cisco equipment

Unanswered Question
Jun 16th, 2009

I have a small WLAN, that I am upgrading with a managed switch (Alcatel OA 4012). I have 4 1120B APs and many 1220B/1231G APs. They work with the power injector, but this switch supports POE. I don't find the "power negotiation" settings in the Web GUI under system config. like Cisco's documents suggest. Can anyone help with this?

Thank you

I have this problem too.
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Robert.N.Barrett_2 Tue, 06/16/2009 - 09:39

If your AP firmware is up to date, go to the System Software -> System Configuration page via the AP's browser interface.

From the CLI, it would be:

[no] power inline negotiation {prestandard source |

injector{installed | override | MAC address}}

Syntax Description

Defaults

The manufacturing default configuration is power inline negotiation prestandard source. If your switch supports Intelligent Power Management, you should change this setting by using the no power inline negotiation prestandard source command.

prestandard source

Specifies that the Cisco switch is running older software that does not support Intelligent Power Management negotiations but is able to supply sufficient power to the access point.

injector installed

Specifies that a power injector is used to supply sufficient power to the access point and that the Cisco switch is running older software that does not support Intelligent Power Management.

injector override

Specifies a power injector is supplying power and the access point is configured to override all inline power checks.

Caution:When using the power inline negotiation injector override command, a power injector must always be installed to prevent a possible overload condition with an underpowered power source.

injector MAC address

Specifies that a power injector is supplying power to the access point and the access point is connected to a new switch port with the indicated MAC address. Enter the MAC address (in xxxx.xxxx.xxxx hexadecimal format) of the new switch port where the power injector is connected.

Note:This command should only be used when you move an access point and power injector to a different switch port.

churcht39 Tue, 06/16/2009 - 10:46

I am running 12.3(8)JEC3 with 12.2(4)bootloader on the 1120s. The 1231s are running 12.3(8)JEA3 with 12.2(8)bootloader.

In the browser interface there is no options for power negotiation. I don't know why they don't have that option.

Thanks

rob.huffman Wed, 06/17/2009 - 04:45

Hi Troy,

This good reference from Robert is available only on the LWAPP deployment integration with Wireless Lan Controllers and would not be applicable for these AP models :(

The problem here is that these "older" AP models (1121/1220) can not be supported with 802.3af PoE.

Most Cisco Aironet access points use inline PoE from power injectors or Cisco powered EtherSwitches, but the Cisco Aironet 350, 1100, and 1200 series access points do not directly support IEEE 802.3af power sources. These access points were designed before the IEEE 802.3af power standard was ratified and use what is termed "Cisco Pre-Standard PoE". Cisco Pre-Standard PoE is not supported on "third party" 802.3af switches.

From this good doc;

http://www.cisco.com/en/US/docs/wireless/technology/poe/technical/reference/Power.html#wp43156

Hope this helps!

Rob

churcht39 Wed, 06/17/2009 - 09:40

So does that mean if I convert them to LWAPP that my POE switch can provide power? I would think that this is a software setting, not so much a hardware issue. I also have some 1231G APs that also do not offer the option (all are autonomous APs).

Thank you!

Troy

rob.huffman Wed, 06/17/2009 - 09:55

Hi Troy,

Sorry man, my explanation was somewhat lacking here. The command that we are talking about here is used for powering "newer" Ap's like the 1131(that requires 802.3af PoE) series on an "older" Cisco pre-standard PoE only switch. It will never help power an 1121 on a 802.3af switch.

You have to keep in mind that all Cisco switches are backwards compatible to support Cisco pre-standard PoE but third party switches never will.

Cheers!

Rob

churcht39 Wed, 06/17/2009 - 11:17

Thank you, I wish I would have researched this better before I bought that Alacatel 4012 switch. Oh well, it is still a good managed switch, just no POE for my equipment

Thanks to all who posted!

Troy

churcht39 Thu, 06/25/2009 - 08:11

I don't give up so easily, and I was doing some more online research. Is it true that if I change the pinout on my C5e cable to reverse the polarity (pins 4,5 for + and pins 7,8 for -) the older cisco equipment will work with the 802.3af switch?

Sorry to keep bugging you guys, but this sounds reasonable to me.

rob.huffman Thu, 06/25/2009 - 09:56

Hey Troy,

Good stuff!

Funny, I was thinking about your predicament just yesterday! I remembered seeing these "Dongles"

PD-PS-401/CISCO

PowerDsine Power over Ethernet splitters enables easy integration of the Power over Ethernet technology into legacy equipment. Using the same infrastructure, without making any modifications to the end points, already designed devices, such as Wireless LAN access points, Web cameras or IP telephone sets become Power over Ethernet enabled when connected to the active splitter.This product is designed for the following systems:AP350, AP11XX, AP12XX - Wireless Access Points;791X, 794X, 794XG, 796X, 796XG, 7905 - IP Phones.

Check it out, they're pretty cheap.

Cheers!

Rob

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