two AP's with same SSID for coverage

ps56k · 2009-01-23T02:09:20+00:00

Having seen several threads about this type of WiFi coverage issue,I was wondering about having 2 AP's at ends of the houseto provide better coverage....If we have 2 AP's with the same SSID,both connected to the same IP segment,and the DHCP coming from one router,then what are the issues involved ??Not really a roaming issue, but it can be...SO - we have one AP upstairs in the middle of the upstairs bedroom area,and another down in the family room area.Will you "associate" with the strongest signal ?Is that always true ? In the middle, can you ping-pong between them ?For the most part - you are either upstairs or downstairs.What happens if you are downstairs, and then walk up to your roomto do homework - will you re-associate with the closer & stronger AP ?Just wondering how this could/would/should work with multiple AP'sall on the same channel & SSID ?

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Aaron Leonard 17 years ago

~ >But I would say that, in our medium-large enterprise installations, ~ >at least 80% of our installed APs are dual-band (except for in those ~ >countries that don't allow 5GHz wifi.) ~ ~ Also 4.9GHz for public safety. The fairly small incremental cost of ~ adding the 2nd wireless PcCard is nominal compared to the cost of the ~ access point. However, I wonder how many of those medium-large ~ enterprise installations actually use 5.8GHz? WiFi Hopper and various ~ sniffers (Kismet and Kismet-Newcore) will display and filter by 802.11 ~ mutation. I've sniffed with these around industrial districts and ~ haven't really found much traffic. Plenty of point to point links, ~ some SSID broadcasts, but very little client traffic moving. The AP's ~ may be out there, but they don't seem to be using 5.8GHz.

5GHz has definitely reached critical mass in the enterprise. It's the band of choice for 802.11 phones (our 7921/7925s). And enterprise grade laptops pretty much all now come with dual band NICs.

We are pushing 5GHz especially for 802.11n. For obvious reasons,

40MHz wide channels in 2.4GHz make zero sense in any dense deployment. While the relatively wide open spaces of say the UNII-2 Extended band would accommodate a few such channels quite nicely.

~ Back around 2000-2002, after the dot com bust, many companies gave ~ their layed off employees a severance bonus in the form of surplus ~ computing equipment. Convincing a home users that a RAID 5 redundant ~ everything server, some giant Cisco router, a 48 port ethernet ~ switches, and such were not suitable for the average home user, was ~ ummm.... awkward. Yell louder.... I can't hear you over the fan ~ noise. Why is it 120F in here? Why is everything so big? Anyway, I ~ had lots of experience deploying enterprise grade hardware in several ~ home environments. The trick was to get paid before the electric bill ~ arrived.

True that. Although our APs aren't so bad. I have an 871W and an AP1131 (in addition to my trusty WAP54G) at home, and if they were visually or audibly unacceptable in any way, I am confident that my wife, who is hypervigilant in those regards, would have called them out.

~ Favorite enterprise hardware questions from the home user... where is ~ the on-off switch? Why is it on the rear panel where I can't get to ~ it? What do you mean it never gets turned off?

Why, our APs' on/off switch is the software settings on the PoE switch, of course ... what could be simpler?

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Jeff Liebermann 17 years ago

5AM, can't sleep, mildly drugged... let's see if the brain is still functional.

Yep, the logic is compelling. I note that the user has the choice of "preferred" band and mode. However, the default seems to be which ever band produces the strongest signal:

Support mode - 802.11a - 802.11b/g - Autosensing, 802.11b/g preferred over 802.11a - Autosensing, 802.11a preferred over 802.11b/g - Received signal strength indicator (RSSI) (default)

I don't recall the exact terms of the compromise worked out between the parties involved. Both the 871w and AP1131 are relatively small boxes, with minimal wiring, no fan, little heat, and are fairly easy to hide. Unless your network wiring looks like this:

I don't think there would be any complaints.

However, the "enterprise quality" equipment I was trying to install in a home environment came from a dot com that owned their own servers and rented rack space at a server farm. I don't recall the model numbers, but suffice to say that the hardware was big, ugly, noisy, hot, and expensive to operate. While I'm sure this was not the intent of the original statement suggesting the use of "enterprise quality" equipment in the home, it does offer and extreme example.

I left out one question.... Why do I need a computer just to turn this thing on and off? The point is that the typical home user has different expectations on how to install, operate, and configure the equipment. I ran into this problem trying to configure a 7690 IP phone. Without a TFTP server, it was futile. There are some rather fundamental differences between a locally configured IP phone, and one that requires an IT department to manage the downloadable configuration from a permanent server. There's also no (easy) way to save the settings.

Then, I noticed that there was no backlighting on the 7690 LCD display. That makes sense in an "enterprise" environment, where the lights are never turned off during working hours. However, at home, trying to dial a number at night requires a flashlight. I also have a Linksys/Sipura SPA921 with exactly the same issues.

Sure, bring the "enterprise hardware" home and it can be made work. Just be prepared for some oddities and ummm.... inconveniences. Ask your wife what she thinks of an IP telephone that doesn't light up in the dark.

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Aaron Leonard 17 years ago

~ >~ Favorite enterprise hardware questions from the home user... where is ~ >~ the on-off switch? Why is it on the rear panel where I can't get to ~ >~ it? What do you mean it never gets turned off? ~ >

~ >Why, our APs' on/off switch is the software settings on the PoE switch, of ~ >course ... what could be simpler?

Let me while I'm at it highlight why this arrangement might make sense for a large enterprise ... they can for example program their switch to turn off all the PoE ports to all the APs at 8 p.m. then turn them back at say 6 a.m. ... saving say 400 * 10W * 10 hrs = 40kW hr / day.

Well, I guess that's just 5 bucks per day, but then there's "greenie points" and some security benefit to consider too.

~ I left out one question.... Why do I need a computer just to turn this ~ thing on and off? The point is that the typical home user has ~ different expectations on how to install, operate, and configure the ~ equipment. I ran into this problem trying to configure a 7690 IP ~ phone.

("7960" I supppose)

~ Without a TFTP server, it was futile. There are some rather ~ fundamental differences between a locally configured IP phone, and one ~ that requires an IT department to manage the downloadable ~ configuration from a permanent server. There's also no (easy) way to ~ save the settings.

Good point, absolutely. Look at our nifty little 7921 VoIP phones. If you can get past the price tag, you're looking at not merely deploying a TFTP server, but a Cisco Call Manager (no SIP supported), and maybe an Avalanche NMS system. Probably doesn't make sense for a humble cabin in the Santa Cruz hills.

For enterprise devices such as our phones and APs (here I'm talking about "big" Cisco not Linksys), the infrastructural overhead of bringing up the first unit is huge. Where you win is the incremental cost (esp. when it comes to deployment and maintenance personnel costs) of the 1000th unit.

So ... with all that infrastructure set up, now I can take my 7921 phone home from the office to my house, and it (usually) "just works" to associate to our corporate WPA/TKIP/EAP-FAST SSID and connect up to Cisco's core Call Manager in San Jose, and now my office phone # shows up on it in Tucson AZ.

~ Then, I noticed that there was no backlighting on the 7690 LCD ~ display. That makes sense in an "enterprise" environment, where the ~ lights are never turned off during working hours. However, at home, ~ trying to dial a number at night requires a flashlight. I also have a ~ Linksys/Sipura SPA921 with exactly the same issues. ~ ~ Sure, bring the "enterprise hardware" home and it can be made work. ~ Just be prepared for some oddities and ummm.... inconveniences. Ask ~ your wife what she thinks of an IP telephone that doesn't light up in ~ the dark.

We learn, if gradually. The follow-on 7970 phone has a nice big bright color touchscreen.

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