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ASK THE EXPERT- POWER OVER ETHERNET SOLUTIONS

Welcome to the Cisco Networking Professionals Ask the Expert conversation. This is an opportunity to discuss Power over Ethernet Solutions. Marcus is a Senior Manager, Enterprise Technical Marketing, and his team focus on end-to-end enterprise network design, including LAN, WAN and Metro. Marcus has been with Cisco for six years and has worked closely with the development and deployment of the Catalyst product line as well as helping customers understand the best practices for network design and deployment. Remember to use the rating system to let Marcus know if you have received an adequate response.

Marcus might not be able to answer each question due to the volume expected during this event. Our moderators will post many of the unanswered questions in other discussion forums shortly after the event. This event lasts through March 12. Visit this forum often to view responses to your questions and the questions of other community members.

16 REPLIES
New Member

Re: ASK THE EXPERT- POWER OVER ETHERNET SOLUTIONS

Hi Marcus,

We have AVAYA 4620 IP-Phones connected to Cisco Catalyst 4500 inline power modules. But we came to know that the Cisco does not support these phones ( the power output is not compatible). What is the suggested workaround for this. We are a complete Cisco network but had to go for Avaya IP phones due to availabilty.

Regards,

Vinod Morsa

Cisco Employee

Re: ASK THE EXPERT- POWER OVER ETHERNET SOLUTIONS

Hi Vinod,

The reason is most likely that the Catalyst 4500 modules that you have support the Cisco in-line power, not the line cards that support the standard 802.3af version. Hence the power output incompatibility. The recently announced Catalyst 4500 modules will support 802.3af and will power the Avaya phones. You can check out:

http://www.cisco.com/en/US/netsol/ns340/ns394/ns147/ns412/netbr09186a00801f4329.html for more information.

Regards,

Marcus

New Member

Re: ASK THE EXPERT- POWER OVER ETHERNET SOLUTIONS

Hi Marcus,

I have a question. I notice that Cisco have introduced several new cards for the 6500 chassis, including the new WS-X6148-21AF. I do not understand how you can be providing power over the spare pairs when the RJ21 "Banjo" connector from the cards' faceplate only carries the data wires (1,2,3,6) to the patch panel? Surely a patch panel cannot be the answer since you'd then be inserting the power by another means - not from the card. Can you please explain what happens here? Any URL's I could read would be great.

Another thing. I notice that on this series of new cards you have continued with the 2q2t transmit queuing structure. I find this surprising on a supposed "voice" card since Cisco nearly always recommend a priority queue for voice (indeed, even the IP phones have a Prioroty queue). In order to get the priority queue for voice feature with RJ 21 connectors you have to go up to the [very expensive] WS-6548-RJ21. This card does not do PoE. Do Cisco have any plans for a RJ21 card that has priority queue AND PoE? This would be a very welcome card for several customer I have come across.

Thanks Marcus.

Steve

New Member

Re: ASK THE EXPERT- POWER OVER ETHERNET SOLUTIONS

Hmmmmm, read the spec Steve....

I see that ir says that power is delivered over the inline pairs!! However, the rest of my question I am still concerned about [regarding .3af and RJ21 with priority queue).

Best regards,

Steve

Cisco Employee

Re: ASK THE EXPERT- POWER OVER ETHERNET SOLUTIONS

Hi Steve,

Can you point out the reference for the 2q2t queue structure on the new cards? To my knowledge, all the 6500 line cards support the priority queue.

New Member

Re: ASK THE EXPERT- POWER OVER ETHERNET SOLUTIONS

Hi Marcus,

Here is the URL that'll tell you about the queue structure on the various line cards:

http://www.cisco.com/en/US/products/hw/switches/ps708/products_data_sheet09186a00800923be.html

The WS-X6148-21AF is the new AF card that does not do priority queue. Infact, there are quite a few wiring closet class cards on the 65xx that don't do priority queue. I have come across several customers that have Telco connectors (RJ21) that wanted PoE AND priority queue. Cisco don't do such a card for the 6500 chassis - a great pity. There is a heck of a lot of RJ21 Telco in the UK and Europe.

Thanks for replying to me Marcus.

Best regards,

Steve

Cisco Employee

Re: ASK THE EXPERT- POWER OVER ETHERNET SOLUTIONS

The line cards that do not include the priority queue are those that have been available for quite some time now. What is incremental is the 802.3af daughtercard that incrementally adds power. At this time, the RJ-21 card that supports the priority queue is the WS-X6548-RJ-21

New Member

Re: ASK THE EXPERT- POWER OVER ETHERNET SOLUTIONS

I have an application where I would like to provide PoE to some devices which are not PoE enabled, perhaps thru some kind of adapter, DC-DC convertor, or similar. So long as the power requirements are sufficiently low, can you suggest how one might go about implementing this? Just consider this a theoretical concept discussion and not a request for a supported product. I can imagine, for example, an in-line power extractor (opposite of a power inserter) with configurable output power (V, A) settings and circuitry to handle the negotiation with the PoE switch. Any ideas?

Cisco Employee

Re: ASK THE EXPERT- POWER OVER ETHERNET SOLUTIONS

Interesting application! What I'm imagining is that, instead of the power cord going into the wall, it goes into this adapter. The adapter would then pull the power from the switch.

From a theoretical standpoint, the adapter would be the powered-device, not the device you want to provide power to. If that adapter supports 802.3af, then it would be possible to accomplish what you want. That device would have to determine how much power the end-device needs and then act as the intermediary to the power source equipment.

I'm not familiar with any products on the market that do that, but it isn't a bad idea!

New Member

Re: ASK THE EXPERT- POWER OVER ETHERNET SOLUTIONS

Hey Marcus,

My name is Tony Buckley, I'm currently working on putting up a network replacing Netopia's and Spannet 2500's. I'm replacing these WAN devices with Cisco 2621XM routers and Catalyst 2950 switches. I have a triangle WAN (e.g., point A, point B, point C). B is my focal point where everyone of my users get to the internet.

My problem is this: I set my WIC's at point B(two, one pointing to A and one pointing to C. This is true for each site (A to B&C, C to A&B)). The ip addresses are WIC 0/0 192.168.20.2, WIC 0/1 192.168.40.1 for B location. WIC 0/0 192.168.20.1, WIC 0/1 192.168.60.2 for A location. WIC 0/0 192.168.40.2, WIC 0/1 192.168.60.1 for C location. A&C talk on 60.0, A&B talk on 20.0 and B&C talk on 40.0. They are able to speak okay.

My Switches are 192.168.3.3 at A location, 192.168.1.2 at B location and 192.168.2.3 at C location.

My Internet WAN device is 192.168.1.1 to get out.

My problem is that I can't get location A & C to get out to the internet. I setup NAT for my 3.0 network and 2.0 network, I have my file servers default-gateway at 192.168.1.2. I can ping all the way to the file server, but I can't get on the internet. Can you help me in ANY way determine what is happening and why I can't get out. Your suggestions would be greatly appreciated.

Cisco Employee

Re: ASK THE EXPERT- POWER OVER ETHERNET SOLUTIONS

Hi Tony, I'm not sure I can help you on this one. You might want to try the LAN Switching and Routing Forum under Network Infrastructure at

http://forums.cisco.com/eforum/servlet/NetProf?page=netprof&CommCmd=MB%3Fcmd%3Ddisplay_messages%26mode%3Dnew%26location%3D.ee71a04

Regards,

Marcus

New Member

Re: ASK THE EXPERT- POWER OVER ETHERNET SOLUTIONS

Thanks for re-directing me.

Tony

New Member

Re: ASK THE EXPERT- POWER OVER ETHERNET SOLUTIONS

Hello Marcus,

Is there any cisco document stating the differences between Cisco PoE and IEEE802.3af together with a roadmap of product updates for IP phones and LAN switches when possible?

Why does the command show power inline power gives power consumption at 42V instead of the nominal 48 Vdc ?

Cisco Employee

Re: ASK THE EXPERT- POWER OVER ETHERNET SOLUTIONS

Hello, The best resource to have a look at is http://www.cisco.com/en/US/netsol/ns340/ns394/ns147/ns412/networking_solutions_white_paper09186a00801f4325.shtml. That provides some information about the differences between the two.

Regards,

Marcus

New Member

Re: ASK THE EXPERT- POWER OVER ETHERNET SOLUTIONS

Hi,

Would 802.3af PDs work with Catalyst 3524-PWR-XL (pre-standard power) switches?

From my reading it seems that strictly 802.3af devices won't return the Fast Link Pulse back to the switch.

We are in process of migrating away from the 3524s, but there is a timing issue (purchasing PDs before the switch migration is complete).

Thanks,

Scott

New Member

Re: ASK THE EXPERT- POWER OVER ETHERNET SOLUTIONS

Hi Marcus

SRW 224G4P. I know it has End of life, but customers will still use it for the next 1,2 years.

1. POE power in question now - Can config or solution be found for the following use?

2. Devices connected to first 12 ports of SRW 224G4P.

3. POE is enabled and turned on for these 12 ports.

4. When SRW 224G4P power is turn on at the start of day, power is sent out immediately from these 12 ports to the connected devices.

5.  POE power send out is good but, it sends power and then off. then 2 seconds later, power sends out again. then off.

6.  This power on off cycle goes on 4 times in total, lasting 1.5min - 2min time.

7.  AFter 2min, power stays stable all the way.

I worry this will spoil connected devices, due to power on n off 4 times a day, 7 days a week whole year round.

I worry that the new SFE 300 series switches will do the same. Customers will JUMP!!!!

Kindly advise if there is  a way round without physically disconnecting the Cat5 cables.

Regards

Adwin

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