802.3af Compatibility with IP Phones, 3524PWRXLEN, and 3Com NJ200

[NPT_2]

There is a particular location where we would like to put a couple additional IP Phones (7960's) but in this particular location it is beyond the 300 foot Ethernet Distance Limitation from the MDF with the multiple 3524PWR Switches and Battery Backup Systems. Space is an issue or we would just put in another switch and battery system (this would also be expensive for just 2 phones). What would be ideal in this situation would be a repeater or switch that would run entirely off of the PWR provided by a single PWR Switch port on the 3524PWR Switch. The repeater could be put midway between the 400 foot distance and provide runtime in a power failure from the 3524's and batteries there. I found a product that I thought would do this but I am not sure. 3com makes a model NJ200 Network jack that has 4 10/100 Ethernet ports and can be powered directly from a PWR Switch. However I am being told that it could forward that power to the 4 ethernet ports but only if the Cisco Devices are 802.3af compatibile, which I am also being told they are not. Has anyone done anything similar to this or know whether this could work? Or if you have any other product recomendations for this situation that would be great too. We could go 1 to 1 repeaters rather than switches if they could be powered by the 3524PWR and also provide power to the IP phones.

[andyirving]

Have you looked at a Mid Span solution. This would uses the unused pairs on the UTP and is one of the 802.3af "standards". PowerDsine have a good range and supply vendors such as Avaya, Nortel and 3Com. They have a 1 port Power over Ethernet product that should do the job.

http://www.powerdsine.com

[NPT_2]

I am looking at that product now. The only issue I see, is that that 1 port product looks like a hub and not a switch, and thus would not act as a repeater. However, I am emailing powerdsine's tech support for clarification. Perhaps they have another product that will work in this situation. Do you know of any other vendors that are providing similar products as well?

[DAVE GENTON]

A hub is not much more than a repeater ! A hub is basically a layer 1 device repeating the signal it receives on one port out all others. A switch is layer 1 and layer 2 (and then some for others).

-d

[erik.stillman]

Hi,

What did you end up doing in the end?

We have a similiar situation here.

Thanks,

Erik.

[NPT_2]

We ended up creating an additional idf with a fiber link to the mdf with another PWR Switch. Unfortunately we did not really find a product that would work otherwise. If you run into one, let me know, it could come in handy in several other situations too.

[erik.stillman]

Thanks. I think we're going to try the NJ200 by 3com; unless you know for certain that one port on the 3524 can power only one device?

[NPT_2]

As far as I know Cisco has yet to release any 802.3af complient devices, they use proprietary power over ethernet. So the any Cisco PWR switches in your MDF would not be able to actually power the NJ200, only provide the data connectivity, and you would have to plug the NJ00 into a external power outlet. It could still cover the repeater function but would require a power source. Once Cisco releases a 802.3af complient switch you should be able to use it to power the NJ200's. I think Cisco has some switches shipping now that will eventually be upgradable to 802.3af but I don't think they can be yet. If in doubt contact the TAC or your Cisco sale rep or engineer, they should be able to verify this. Good Luck

Jim

[tmitchell]

Why couldn't you run cat 5 from the Cisco 3524, at the 3com rewire your rj45 so the power strands match the 3com (standards based) pin out? next, do a similar wire scheme from the 3com to your phone.

Its not Cisco's solution... but it should work.

best regards,

Mitchell

[NPT_2]

If I get you right, you are talking about splicing out the power strands and manually injecting the needed power, such as with a DC power adapter with the apropriate voltages. That actually sounds like a pretty interesting solution that might actually work. I just thought of another option too, Cisco Makes a single port power injector, these run cisco's proprietary power standard, but I wonder if 3com or another vendor makes one that are stardards based, that way you could put the power injector in the main wiring closet connected to the 3524, connected to a power source, and use it to power the remote 3com Network jack. Also perhaps just use 2 3com network jacks, one in the main closet with external power, and one at the remote location powered via standards based power over ethernet. I'm really looking forward to that standard being finalized and Cisco actually adopting it.

Jim

[tmitchell]

I stand corrected...

[tmitchell]

There are currently two different implementations of in-line powered Ethernet ports in Cisco products. The first uses the same two pairs of wire over which the Ethernet signals are carried (pins 1, 2, 3, 6), while the other uses the two unused Ethernet pairs (pins 4, 5, 7, 8). The IEEE 802.3af committee will eventually standardize in-line power over.

URL http://www.cisco.com/en/US/products/hw/phones/ps379/products_tech_note09186a00801189b5.shtml

In-Line Power Patch Panel

The in-line Power Patch Panel (IPPP) uses the unused Ethernet pairs to provide in-line power. The IPPP has four rows of RJ-45 connectors each with 24 ports in a row. The top two rows are the powered ports used to connect to the end device (for example, a 79xx IP Phone). The bottom two rows are used to connect to the Switch which will be providing the Ethernet connectivity.

Internally, the IPPP will directly connect the Ethernet pairs from the bottom switch port to the corresponding phone port on the top. The in-line power patch panel does not interfere with pins 1, 2, 3, and 6 in any way. It does not monitor link and does not care about speed/duplex, because it is completely passive.

The phone discovery algorithm for the IPPP is similar to the method used on Catalyst switches as explained in the previous section. It relies on the fact that the phone will loop back a special signal that the IPPP sends on its ports. In this case, however, the unused pins 4, 5, 7 and 8 are used to detect IP Phones. If an IP Phone is detected, these pins (wire pairs) are also used to provide power.

The following method for detecting that an IP Phone is connected to a 10/100 Ethernet port is used by the The In-line Power Patch Panel (WS-PWR-PANEL).

The IPPP starts the phone discovery sequence at port 1.

The IPPP sends a 347kHz loopback tone out port 1. The IPPP listens for 50ms to to determine if the loopback tone is being forwarded back by a device that is connected to the port. Only devices that are expecting to receive power on these pins will forward the loopback tone to the sending device (the IPPP in this case). The IPPP must detect 16 transitions within a 50ms period of time to verify that it is sensing the correct loop back tone and not an anomaly.

If the IPPP verifies that this received signal is the correct one, power is enabled on the port. If the signal is not correct the IPPP moves on to the next port and starts the process over again.

The IPPP continuously cycles through the ports repeating the above steps for each port.

Each port that is supplying power is polled for 50ms every 600ms to ensure there is still a device attached. This ensures that power is turned off at the port if the device that required it has been disconnected.

Tmitchell

847 274-3083

[vinodhjoseph]

Dear All

We are running a call centre in india with AVAYA Ip Solutions. LAN is completely engineerd with CISCO Devices whre we recently bought 10 Nos. for WS-PWR-PANEL to power up AVAYA/NORTEL IP Phones. This has been told by the leading HP reseller out here in Delhi.

We knew that AVAYA IP phone just need 48 V DC on pair 7&8 to power up over LAN. And this wouldnt support any Phone discovery algorithms or other varients while the voltage should be at a constant value of 48V.

We enabled WS-PWR-PANEL on blast mode, and we are able to see 48V between pairs 4&7 and 5 & 8 (both). When we interconnect this to an AVAYA Phone, the voltage suddently gets reduced to 9V DC. I hope this is becoz of IPPPs phoen discovery algorithms and associted CDP. IS there a wasy to disble CDP on PWR-PANEL and completely by pass phone discovery ?

Would appreciate if some one could help us in this reagrd with some wuick views..

thanks

VJ

[vinodhjoseph]

Couple more info.

01. When we enable Bast mode , the status LED on WS-PWR-PANEL get on stationary "RED" . Sint that Common ?

02. The port by which AVAYA IP phone connected shows on continouse binking, does that mean that it looks for phone discovery ?

Above all, how do i make the scenario thru , expcets your expert analysis..