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5508, 3500, 7.0, and many clients

Hello,

I'm looking for advice on adding/replacing our APs and upgrading firmware.

We have 36 3500i APs, a WCS, a 5508 controller, and a 3310 MSE, all running 7.0.230.0. At any given point we have around 800 clients connected across 3 WLANs. We have been having performance issues (including slowness and no connection), mostly because there are a bunch of APs out there with 30-50 clients, a couple can even get up to 70. I know Cisco says the 3500 supports 15 clients. It seems 25 clients is about the max that we can actually have without issues.

We are a high school with about 100 employees during the day and 1100 students. We were told this spring to open the Wifi to students, so we gave them an SSID with webauth. Stable Wifi is very important in general since we force students to use VMware View desktops on lab computers and encourage employees to do the same, which most do. A common complaint is that the virtual desktops are very laggy or they lose connection.

In addition to high Wifi client count, we also had all Wifi clients, plus a few dozen servers/network infrastructure devices, plus 350 virtual desktops, plus about 50 hardwired devices attached to the MDF... all in one VLAN (about 2000 8-day leases in the DHCP scope). Last week I made 3 separate Wifi VLANs for employees, other school-owned equipment, and students to ease up that problem. Additionally, while the WLC itself was already using LAG, I enabled it on the Juniper switch (FYI there is an option in the Juniper GUI to not use LACP) and increased the links from 2 to 3.

But I'm still concerned about the client saturation around the APs. We're considering buying several of the new ones that will handle 128 clients, putting them in key areas, and relocating existing APs elsewhere to increase AP saturation. We'd like to have AC to futureproof the new ones. The 2700 looks like the best choice being AC and having ClientLink 3.0 and HDX. What I'm wondering is, would it be worth choosing a 3700 over the 2700? I know the 3700 can receive upgrade modules for later revisions of AC, but to me that's all a moot point given a one gigabit connection going back to the switch. The 3600 seems like an OK option to save money now, and potentially put later revision AC modules in it (or is it limited to wave 1?) if the need arises. But it being ClientLink 2.0 is a drawback. I was thinking about the 2600 if we wanted to forget about AC and save money now.

Also regarding APs, I'm unclear about the purpose of external antennas. Our 3500s are internal. Are the external ones supposed to help saturation issues, or just increase range/throughput? How effective are they? Is there a significant price difference?

Then I got to thinking about upgrading the firmware. I've read that the newer releases are supposed to improve saturation issues. How much so? Enough to potentially alleviate the need for more APs, or at least the most expensive ones? Should I go for 7.6 or 8.0? I've seen Cisco employees here mentioning an 8.0 MD coming very soon so maybe that's the best bet (if timely).

Thank you for any advice you might have!

1 ACCEPTED SOLUTION

Accepted Solutions
VIP Purple

Hi Cisco given value is per

Hi 

Cisco given value is per radio.

Remember that 5GHz has more channels & client can bonds channels to get increased throughput.

As 3500 AP 2x3:2 (ie 2 Tx & 3 Rx antenna with 2 Spatial stream) you can get 300 Mpbs PHY on 5GHz with 40MHz channel width. Assuming 50% efficiency, you can think of 150Mbps as throughput. So depend on how much per user bandwidth you want to give  you can estimate how many clients you can allow. Say if it is 5Mbps per client, then you can go for 30 clients max.

In 2.4GHz band, you can get 130Mbps as PHY, on the same assumptions you could have 65Mpbs throughput & for the same bandwidth per client you can go upto 13 clients max.

When it comes to best practice numbers we keep some margin as well (reduce those numbers little bit).

Here is 3500 data sheet for the PHY values taken for the above calculation.

http://www.cisco.com/c/en/us/products/collateral/wireless/aironet-1250-series/data_sheet_c78-594630.html

Like this you can estimate number of client you could have in each radio.

HTH

Rasika

**** Pls rate all useful responses ****

5 REPLIES
VIP Purple

I think 3700 would be the

I think 3700 would be the best if you could afford it. Here is the 802.11ac AP comparison & you can see VDI mentioned for 3700. Also make sure you have right switches to power these 3700 as it require 18.4 W (POE+ or 802.3at)  for the proper operation. 

http://www.cisco.com/c/en/us/products/wireless/buyers-guide.html#~indoorac

Here is the 3700 deployment guide which cover all the aspect of the AP (power, antenna, etc)

http://www.cisco.com/c/en/us/td/docs/wireless/technology/apdeploy/7-6/Cisco_Aironet_3700AP.html

Regarding firmware, your 8.0MR1 is due to release in coming weeks. If you are upto a challenge you can go for 8.0MR1 (otherwise only option is 7.6.130.0). You should refer the release notes of WLC code that you can find here

http://www.cisco.com/c/en/us/support/wireless/5500-series-wireless-controllers/products-release-notes-list.html

Also make sure you upgrade your FUS to 1.9.0.0 with these software upgrade. This process will take 30-40min downtime to your wireless & make sure you get enough outage organised. Also do it via CLI. There is no preference WLC software upgrade first or FUS upgrade first, you can do either way. Here is the release notes for FUS upgrade

http://www.cisco.com/c/en/us/td/docs/wireless/controller/release/notes/fus_rn_OL-31390-01.html

 

HTH

Rasika

**** Pls rate all useful responses ****

New Member

Thanks for all the info,

Thanks for all the info, Rasika. I missed the VDI part about the 3700. That's definitely a consideration. We have Juniper EX4200 and 3300 switches so PoE isn't a problem there, however we do use power injectors that came with the 3500s for a couple 3Com switches. I'll have to check them out for wattage. Although I just read that if you only supply 15.4 watts, they'll simply switch to 3x3 mode and will utilize 4x4 when 18.4 is available.

What makes the switch to 8.0.100.0 a challenge?

My next concern is the WCS. Will it even be able to manage the WLC with 7.6 or 8.0 since it's so outdated? If we want to deal with the WCS, as I understand we have to first switch to NCS, then to CPI. And NCS comes as a virtual machine and the configuration file can be loaded in to the NCS, then NCS can be upgraded to CPI. What are the licensing implications with this? Will the WCS license not apply towards CPI? What's the cost of a license (presently 1000 users but would consider increasing if we have to upgrade anyway)?

VIP Purple

What makes the switch to 8.0

What makes the switch to 8.0.100.0 a challenge?

Since this is the first release of 8.0 train, it is too early to say how good or bad. That's why I said it is a challenge. But if MR1 comes in coming weeks it is safe to go for that.

Regarding 15.4W power, yes AP will work with reduced number of radio chains. (3x3).

Will the WCS license not apply towards CPI?


I would think best way to is purchase those migration license from WCS to Prime & build your CPI & install those licenses. Please check with your Cisco AM about pricing.

 

**** Pls do not forget to rate our responses if you find them useful ****

HTH

Rasika

New Member

Thanks again for the info.

Thanks again for the info. One more question: When Cisco gives supported client counts, is that total per AP, or is it per radio (of which our 3500s have 2)? In other words, looking at the client count, is it acceptable for an AP to have 14 + 12, or is the total of 26 a no-no?

VIP Purple

Hi Cisco given value is per

Hi 

Cisco given value is per radio.

Remember that 5GHz has more channels & client can bonds channels to get increased throughput.

As 3500 AP 2x3:2 (ie 2 Tx & 3 Rx antenna with 2 Spatial stream) you can get 300 Mpbs PHY on 5GHz with 40MHz channel width. Assuming 50% efficiency, you can think of 150Mbps as throughput. So depend on how much per user bandwidth you want to give  you can estimate how many clients you can allow. Say if it is 5Mbps per client, then you can go for 30 clients max.

In 2.4GHz band, you can get 130Mbps as PHY, on the same assumptions you could have 65Mpbs throughput & for the same bandwidth per client you can go upto 13 clients max.

When it comes to best practice numbers we keep some margin as well (reduce those numbers little bit).

Here is 3500 data sheet for the PHY values taken for the above calculation.

http://www.cisco.com/c/en/us/products/collateral/wireless/aironet-1250-series/data_sheet_c78-594630.html

Like this you can estimate number of client you could have in each radio.

HTH

Rasika

**** Pls rate all useful responses ****

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