Solved: Further help for a 'Newbie'...

duncangrant · ‎11-30-2005

Hello again Folks,

I posted here a few days ago (Pls help a 'Newbie', 27th November) and thanks to the prompt reply, I have now sucessfully configured my first Aironet 1200!

I have another five to set up (for the same site) and I am now considering the best way to proceed with the whole installation..

At least two of the additional 1200's will be in radio range of the first 'root' 1200. Now should I set these two as repeaters or as other 'root' devices? The three remaining 1200's will not be in radio range of the original 'root', but will be in range of other 1200's.

Can a 'repeater' talk to another 'repeater' that will then talk to a 'root'? (i.e., a 'bucket brigade line'...) or can a 'repeater' only talk to a 'root'?

If a device (in this case a HP IPAQ) is in radio range of two or more AP's, what happens? Does the device pick the AP giving the strongest signal, or do all the AP's try to respond to the device and then cause interference?

What if I install a repeater between two 'roots' - is this a good idea?

The installation is in a large glasshouse (with a lot of steel framework) - all AP's will be in 'line of sight' of each other. I have a Cisco 12dB gain antenna for each 1200.

The first 1200 that I have set-up is easily giving coverage of about 1/3 of the glasshouse with very good signal strength, so the five additional AP's should swamp the site with RF - is it bad practice to have too many AP's in a given area, or would this be OK but just overkill?

Sorry to ask so many basic questions, but I need to learn very quickly about what I can and can't do with the 1200's...

scottmac · ‎11-30-2005

You can copy the config (as a template) from the working 1200 and copy it into the remaining units.

Once loaded, you'd want to edit the IP address, and probably the channel assignment.

If you are using it for 802.11g, the three non-interfering channels (for the USA) are 1, 6, and 11. If you use anything in-between within range of a unit using channels 1, 6, and/or 11, then that unit will interfere with the channels on either side (example: using channel 8 will interfere with channels 6 and 11).

Using 12db antennas everywhere is probably not a good idea from a security standpoint, and any two units that can see each other on the same channels (or intermediate channel) will interfere and (at the least) slow things down.

This is a case where a good site survey (as in most cases) will give you a better feel for how to cover your area.

For example, you might want a good omnidirectional antenna in the middle of the building, with semi-directional antennas (like a "patch" antenna) on the units located near the corners pointing inwards.

By reducing the scope of coverage (the coverage pattern of the antenna), you can prevent units from interfering with each other and allow you to use the three clear channels and maximize you coverage and wireless throughput.

Using a repeater will reduce your throughput by a little more than half; the repeater works using "store & forward" .... it can't transmit and receive at the same time. Generally speaking, use of a repeater should be reserved for "must use" situations. Chained repeaters is a bad design.

If a single AP is covering 1/3 of the area, you probably do not need a repeater.

Another possibility is to set one or more APs to act as "hot standby" units (only function after a failure of it's neighbor unit).

If there is a wired LAN that all APs are connected to, then you can set up a Wireless Domain which will/may improve your roaming switch-over (the APs talk to each other to coordinate the handover).

Post any remaining questions and we'll try to fill in the blanks for ya.

Good Luck

Scott

View solution in original post

scottmac · ‎11-30-2005