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Emlynfluff 02-14-2007 03:38 PM

Cisco 1221 AP to IP phone phone power issue
 
I am are working on a solution for a county fire service. They
recently have had a sizeable Cisco IP phone rollout, over their ~30
stations.

The next stage is to install phones in their Breathing Apparratus
rooms, which we can't hardwire cat-5 in to. So, we're testing a
solution, using Cisco 1231G AP's, the remote in workgroup bridge mode,
to link via a wireless bridge, back to the LAN. We then plug a Cisco
IP phone eg: 7912G, in via cross-over to the remote AP.

The problem is when I plug a phone in to the Ethernet of the remote AP
via cross-over cable, the phone switches off. This works fine
conecting up my laptop.
If I install a switch between the two devices, plug AP and phone in to
that - it works. Because of the environement in the fire stations,
we don't want to install a switch, we would like to use the cross-over
direct in to the phone. (if possible!)
I am assuming there is some kind of Cisco proprietary Inline power
issue going on here, and the phone switches itself off, expecting to
be powered via Inline?

Customer doesn't want to use a wireless Cisco 7920 - they'd like a
desktop phone, so we're stuck with a wireless workgroup bridge. We
could use another AP, without Cisco Inline, but the 1200 is rugged,
and deisgned for that envirnment, much preferred choice.

How can we get the phone working with the access point, without the
use of a switch?

Any help here would be greatfully appreciated.

Stuart.


Aaron Leonard 02-14-2007 06:24 PM

Re: Cisco 1221 AP to IP phone phone power issue
 
Hi Stuart,

The AP1200 does not *supply* Power over Ethernet (although it can
*consume* PoE. So if you're trying to power your 7912G from the
AP, this can't work.

So you would need to power your phone from a brick plugged into an
AC power source (or some other how supply the phone with the 48VDC
that it requires.)

Regards,

Aaron

---


~ I am are working on a solution for a county fire service. They
~ recently have had a sizeable Cisco IP phone rollout, over their ~30
~ stations.
~
~ The next stage is to install phones in their Breathing Apparratus
~ rooms, which we can't hardwire cat-5 in to. So, we're testing a
~ solution, using Cisco 1231G AP's, the remote in workgroup bridge mode,
~ to link via a wireless bridge, back to the LAN. We then plug a Cisco
~ IP phone eg: 7912G, in via cross-over to the remote AP.
~
~ The problem is when I plug a phone in to the Ethernet of the remote AP
~ via cross-over cable, the phone switches off. This works fine
~ conecting up my laptop.
~ If I install a switch between the two devices, plug AP and phone in to
~ that - it works. Because of the environement in the fire stations,
~ we don't want to install a switch, we would like to use the cross-over
~ direct in to the phone. (if possible!)
~ I am assuming there is some kind of Cisco proprietary Inline power
~ issue going on here, and the phone switches itself off, expecting to
~ be powered via Inline?
~
~ Customer doesn't want to use a wireless Cisco 7920 - they'd like a
~ desktop phone, so we're stuck with a wireless workgroup bridge. We
~ could use another AP, without Cisco Inline, but the 1200 is rugged,
~ and deisgned for that envirnment, much preferred choice.
~
~ How can we get the phone working with the access point, without the
~ use of a switch?
~
~ Any help here would be greatfully appreciated.
~
~ Stuart.


Emlynfluff 02-15-2007 09:56 AM

Re: Cisco 1221 AP to IP phone phone power issue
 
On 14 Feb, 18:24, Aaron Leonard <A...@Cisco.COM> wrote:
> Hi Stuart,
>
> The AP1200 does not *supply* Power over Ethernet (although it can
> *consume* PoE. So if you're trying to power your 7912G from the
> AP, this can't work.
>
> So you would need to power your phone from a brick plugged into an
> AC power source (or some other how supply the phone with the 48VDC
> that it requires.)
>
> Regards,
>
> Aaron


Hi Araon, cheers for the reply.

Yep, I understand the devices are clients receiving Inline power.

The access point has its power supplied by the PSU.
The phone is also using an external power adapter (cube) to supply its
power. I connect external the power to the phone, it boots up, then
connect the cross-over cable in to the phone-AP, the phone switches
itself off.
I believe the phone is doing some sort of Inline power negotiation,
and since the AP also supports this (as a client), maybe they're
getting confused? The phone could think that the AP can supply
Inline power, so the phone swiches off external PSU, and chooses ILP
as a preferred souce?
I can't force the phone to use external power only, ignoring ILP. I
can't disable Inline power on the AP..

Any ideas how to work round this?
I know sticking a switch in between the two devices works. I snipped
the spare pins in the Ethernet cross-over cable, 4,5,7 & 8, but then
read Inline power uses the same as Ethernet - damn it! ;) The
spare cat-5 pins are used for the IEEE standard 802.3af, not Cisco
proprietary ILP.

Stuart.


Aaron Leonard 02-15-2007 06:19 PM

Re: Cisco 1221 AP to IP phone phone power issue
 
On 15 Feb 2007 01:56:15 -0800, "Emlynfluff" <stu@kerridge.com> wrote:

~ On 14 Feb, 18:24, Aaron Leonard <A...@Cisco.COM> wrote:
~ > Hi Stuart,
~ >
~ > The AP1200 does not *supply* Power over Ethernet (although it can
~ > *consume* PoE. So if you're trying to power your 7912G from the
~ > AP, this can't work.
~ >
~ > So you would need to power your phone from a brick plugged into an
~ > AC power source (or some other how supply the phone with the 48VDC
~ > that it requires.)
~ >
~ > Regards,
~ >
~ > Aaron
~
~ Hi Araon, cheers for the reply.
~
~ Yep, I understand the devices are clients receiving Inline power.

~ The access point has its power supplied by the PSU.
~ The phone is also using an external power adapter (cube) to supply its
~ power. I connect external the power to the phone, it boots up, then
~ connect the cross-over cable in to the phone-AP, the phone switches
~ itself off.

Ah, ok, that was the OTHER possible interpretation of your setup
that I entertained from your previous posting. I chose to assume
the one that had the easier explanation :)

So, given this report, my guess is that the phone is being confused
by the CDP from the AP. So I would turn off CDP on the FastEthernet0:

int faste0
no cdp enable

Does this help?

Aaron

---


~ I believe the phone is doing some sort of Inline power negotiation,
~ and since the AP also supports this (as a client), maybe they're
~ getting confused? The phone could think that the AP can supply
~ Inline power, so the phone swiches off external PSU, and chooses ILP
~ as a preferred souce?
~ I can't force the phone to use external power only, ignoring ILP. I
~ can't disable Inline power on the AP..
~
~ Any ideas how to work round this?
~ I know sticking a switch in between the two devices works. I snipped
~ the spare pins in the Ethernet cross-over cable, 4,5,7 & 8, but then
~ read Inline power uses the same as Ethernet - damn it! ;) The
~ spare cat-5 pins are used for the IEEE standard 802.3af, not Cisco
~ proprietary ILP.
~
~ Stuart.


Emlynfluff 02-19-2007 12:32 PM

Re: Cisco 1221 AP to IP phone phone power issue
 

> int faste0
> no cdp enable
>
> Does this help?
>
> Aaron
>
> ---


No joy there, I'm afraid.
I've done a "no cdp run" on the AP, phone still switches itself off
when I plug in the cross-over, and the phone is powered via PSU.

I read that CDP is used after the device has recieved power, so it can
suss out the devices actual power requirements, rather than wasting
some of its limited power budget on a single device.

Thanks for trying, I guess we may have to put a swtch between the 2
devices, which is a shame.





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