Aironet 1300 - External Point to Multipoint

Answered Question

Hi Everyone,


I'm looking to extend my network to cover a number of office buildings on an industrial estate with a distance of 200m max to offer a contended 10Mb internet access service.


If I was to mount the Cisco Aironet 1300 on a mast with a line of sight of the buildings and also provide the same Cisco AP at the client side of this point to multipoint link (mounted externally where possible) would I need any additional hardware? Other then DHCP, DNS servers, switch and router.


Checking I'm not missing something major!


Kind regards,


Tom

Correct Answer by jeff.kish about 8 years 1 month ago

I would recommend the 2506. The 24120 wouldn't be a good fit for this implementation. Such a high-gain omnidirectional antenna may cause the signal to overshoot your remote sites. And yes, the internal antennas for the remote sites will be fine. The internal antenna is pretty strong and can go at least a kilometer. 200m is cake for it.


Best practice is to use the provided antenna cable length, and to not lengthen it. You can certainly do what you're suggesting, but depending on your coax length you'll lose quite a bit of signal doing so.


The double-coax (from the bridge to the power injector) and Ethernet cables can each be up to 100m in length, without any kind of loss. As such, best practice would be:


Antenna mounted to mast

Bridge mounted to mast

<100m of double-coax (runs inside)

Power injector (mounted inside)

<100m of Ethernet (runs to data closet)


If you want to consider installing the bridge in your pop and running the antenna cable up the mast, just find out what kind of loss you'll see. Any coax manufacturer, Cisco or otherwise, will say what the dB/foot or dB/meter is, so you can know exactly how much you'll lose to the cable length. I would recommend against the design though, since you might need a larger antenna which will result in broadcasting a pretty noisy signal.


Jeff

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jeff.kish Tue, 06/09/2009 - 05:16
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Keep antennas in mind. The 1310G can come with an internal 13dB patch (directional) antenna. This antenna would be great for the remote sites, but it wouldn't work well for the root bridge. You'll want to get an omnidirectional antenna for the root. Since the distance is so low, be sure not to get a high-gain one, otherwise your beamwidth will be far too narrow. Don't forget to order the non-internal-antenna model for your root.


The other thing you'll want to consider is how you'll mount the bridges. I'd recommend getting a Cisco 1300 Roof Mount Kit (RMK). This provides the gear for mounting the bridge to a pole. Then you'll need to get a mounting pole of some kind, I've gotten these at Lowe's/Home Depot before (TV antenna aisle). Finally, you need to mount the pole somehow. It's easiest to drill it to the side of a building, but you can also get a non-penetrating roof mount to do it.


Last but not least, you'll need coax cables to run from the bridge down to the power injector that comes with the bridge. Cisco sells this coax cable, but it's sometimes cheaper to contact a cabling vendor for it. You'll then need to run CAT6 from the injector back to your data closet. You need to keep each run to under 100m.


I hope that works for you! This at least takes care of getting the bridges mounted and talking to each other. As for your network behind the bridges, I'll leave that to you :)


Jeff


Hi Jeff,


Thanks for that, I have had a quick look and I think for the root bridge an antenna like the AIR-ANT2506 (or possibly the AIR-ANT24120 but it's quite a bit more expensive!) Do you think that the built in antenna given line of sight over 200m will work without a problem for the client sites? Obviously theirs one way to find out but my time scales are very tight!


The roof mount kit sounds like a good idea.


Also would I be able to mount the Root AP at the bottom of my mast, and then run the cable up the mast to the antenna, and the coax back into my pop next to the mast to where I would locate the injector, + my other equipment? Basically are there limits on the antenna cables? Could I take this one step further and simply have all equipment bar the antenna kept in my pop right next to the mast?


I have a feeling this is going to be a no but I thought I would ask the question!


Kind regards,


Tom

Correct Answer
jeff.kish Wed, 06/10/2009 - 05:46
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  • Silver, 250 points or more

I would recommend the 2506. The 24120 wouldn't be a good fit for this implementation. Such a high-gain omnidirectional antenna may cause the signal to overshoot your remote sites. And yes, the internal antennas for the remote sites will be fine. The internal antenna is pretty strong and can go at least a kilometer. 200m is cake for it.


Best practice is to use the provided antenna cable length, and to not lengthen it. You can certainly do what you're suggesting, but depending on your coax length you'll lose quite a bit of signal doing so.


The double-coax (from the bridge to the power injector) and Ethernet cables can each be up to 100m in length, without any kind of loss. As such, best practice would be:


Antenna mounted to mast

Bridge mounted to mast

<100m of double-coax (runs inside)

Power injector (mounted inside)

<100m of Ethernet (runs to data closet)


If you want to consider installing the bridge in your pop and running the antenna cable up the mast, just find out what kind of loss you'll see. Any coax manufacturer, Cisco or otherwise, will say what the dB/foot or dB/meter is, so you can know exactly how much you'll lose to the cable length. I would recommend against the design though, since you might need a larger antenna which will result in broadcasting a pretty noisy signal.


Jeff

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