Throughput with PRW-INJ-4

[Erik Szlaur]

Hi,

we have Cisco 3702e lightweigh access points that we want  to utilize better. We are using non-cisco POE injectors that can deliver up to 24Watts but we are limited to 100Mbit full duplex between access points and catalyst switches. Is PRW-INJ-4 capable of 1Gbit ?? Does it have any throughput limitation at all? We don't want to use local power supply (such as AIR-PWR-B=) if possible. I skimmed through deployment guide http://www.cisco.com/c/en/us/td/docs/wireless/technology/apdeploy/8-0/Cisco_Aironet_3700AP.html#pgfId-99003aw  but didn't find any information regarding troughput with PoE.

My second question, are PoE+ catalyst switches (such as 2960X) capable of gigabit with PoE+ ??? (we don't have them yet so I can't try)

[Leo Laohoo]

Erik, 

Power injectors do not "dictate" if the link is 10/100/1000 Mbps.  It's the cable.

My second question, are PoE+ catalyst switches (such as 2960X) capable of gigabit with PoE+ ??? 

Unfortunately, your 2960X do NOT support 10/100 Mbps TDR.  However, I have a strange feeling the you've got a cable issue which causes your AP to negotiate only to 100 Mbps.  I've seen this a lot of time in my current AP deployment.

[Erik Szlaur]

Well we use Cat5e mostly. Anyway, I am not sure it has nothing to do with injectors. As I understand the problem, 100Mbit Ethernet uses 2 of 4 pairs while other 2 pairs are used for power delivery. Gigabit Ethernet on the other hand uses all 4 pairs. Therefore injectors need to somehow shift data frequencies on power delivery cables because of interference. I was thinking that our injector is not capable to perform this shifting.

All in all, I just want to know if someone managed to get gigabit link between switch and AP using POE+ (injector or switch) and what equipment was used.

[Leo Laohoo]

Well we use Cat5e mostly. Anyway, I am not sure it has nothing to do with injectors. As I understand the problem, 100Mbit Ethernet uses 2 of 4 pairs while other 2 pairs are used for power delivery. Gigabit Ethernet on the other hand uses all 4 pairs. Therefore injectors need to somehow shift data frequencies on power delivery cables because of interference. I was thinking that our injector is not capable to perform this shifting.

That is correct, Erik.  But what I'm getting at is if your patch cable has a faulty pair of wires, the AP will negotiate to 10/100 Mbps.  I have seen this in a lot of my AP deployment.  

Unfortunately, current 2960X IOS will only support TDR if the link is 1000 Mbps.  

My question is this:  Do you have a 2960S or 3750G/E/X that you can use to do TDR?  The port does NOT need to be PoE.

[Erik Szlaur]

Hi, and thanks for your reply,

yes I have one 2960s available. We also have some specialized devices for testing CAT cables. Altough cables in question can be replaced, I am just trying to figure out what PoE injector to order for next deoployment of 3702e access points. Currently we are using Ubiquiti 48V 0.5A injectors. However, I am not sure if these particular pieces are gigabit capable... propably not, but it may also be a cable issue. I will check it out.

[Leo Laohoo]

Currently we are using Ubiquiti 48V 0.5A injectors. However, I am not sure if these particular pieces are gigabit capable... propably not, but it may also be a cable issue. I will check it out.

I am not an authority on Ubiquiti power injectors but I don't believe injectors can "dictate" the speed of your AP.  It all boils down to cable.  Get a TDR test running using your 2960S.  For GigabitEthernet, you need to have Pair D to be "Normal".  Pair D is the pair that decides whether your link should be running 1 Gbps or not.  If you want to have a read, go HERE.

[Erik Szlaur]

O.K. lets try again. Does AIR-PWRINJ4 support gigabit ethernet? Where can I get technical information such as this http://www.cisco.com/c/en/us/products/collateral/wireless/aironet-antennas-accessories/product_data_sheet09186a00800f927d.html but about PWRINJ4??

Perhaps I should just go for Zyxel PoE12-HP at least they provide easily available technical information.

[Scott Fella]

Can the AIR-PWRINJ4= provide a gigabit link to an access point...Sure it can, but like Leo mentioned, if the access point/powerinjector and switch can't negotiate gigabit, then it will fall back to a lower rate.  If what your seeing is only 100mb full duplex, then it can be your cabling/patch panel or your patch cable that might be an issue.  All 4 pairs need to be terminated properly and usually you can tell that from the patch panel or the access point side if they terminated the ends with RJ45.  See if all 4 pairs are terminated in the proper way, either 568A or 568B depening on what they did.

http://www.cablesplususa.com/pdf/RJ45-Guide.pdf

-Scott