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Occasional Contributor II
Posts: 12
Registered: ‎07-07-2011

WPA2-AES-PSK connectivity/dhcp problems

We have several classrooms with laptop carts with up to 30 laptops. WPA2-AES-PSK is configured and the SSID/key has been configured on the laptops. When the laptops are all turned on, only about 75% of them work. The other 25% either will not connect to the SSID or connect, but can't get a DHCP address. SSID and key are both correct in the wireless profile. If we remove the wireless profile and reconfigure it, then they will work for the rest of the hour. Everything repeats itself after they are shutdown and the next class goes to use them though.

We want to keep WPA2-AES setup so that we can prevent staff/students from bringing in there own devices and getting on our private network. However if it is going to keep doing this then we'll have to find a better solution.
Aruba Employee
Posts: 455
Registered: ‎04-02-2007

Re: WPA2-AES-PSK connectivity/dhcp problems

Any differences with the laptops that can't connect? I'm thinking NIC, driver version, OS, patch levels, etc.? I assume it's always the same clients. Is it always the same location? Are all the APs in the same AP group on the same controller?

-awl
Andy Logan, ACDX
Director, Strategic Account Solutions
Aruba Networks
Occasional Contributor II
Posts: 12
Registered: ‎07-07-2011

Re: WPA2-AES-PSK connectivity/dhcp problems


Any differences with the laptops that can't connect? I'm thinking NIC, driver version, OS, patch levels, etc.? I assume it's always the same clients. Is it always the same location? Are all the APs in the same AP group on the same controller?

-awl




It's happening district wide with A/G/N clients from what I've heard. Laptops are the same model, same image and same drivers. I am not sure if the laptops are the same ones each time or if it varies each time they are booted up. All AP's are still using the default AP group.
Aruba Employee
Posts: 455
Registered: ‎04-02-2007

Re: WPA2-AES-PSK connectivity/dhcp problems

It would be good to double check which laptops are having the issues, and see if it's the same devices. To the district wide, does that mean every site is reporting the issue, or just particular sites? I know this seems painful, but I'm surprised the PSK is causing an issue, usually clients don't have a problem with that. Can you also post some specifics about the clients?

-awl
Andy Logan, ACDX
Director, Strategic Account Solutions
Aruba Networks
Occasional Contributor II
Posts: 12
Registered: ‎07-07-2011

Re: WPA2-AES-PSK connectivity/dhcp problems


It would be good to double check which laptops are having the issues, and see if it's the same devices. To the district wide, does that mean every site is reporting the issue, or just particular sites? I know this seems painful, but I'm surprised the PSK is causing an issue, usually clients don't have a problem with that. Can you also post some specifics about the clients?

-awl




Here's as much detail about the setup as I can recall

- High school building and middle school buildings are on the same subnet. (not good)
- Controller (3600 series) is in the high school building and we have 25 105 AP in the middle school and 40 at the high school or pretty close to that amount anyways.
- Computer models are the following (Brand)(Model)(Wifi Supported)
Dell Latitude D520 (A/G)
Dell Latitude E5400 (G)
HP Compaq 6720s (A/G)
Lenovo Thinkpad Edge E420 (A/G/N)
- Both sites are reporting the issue. The wireless G client are suffering more slow downs than the A/N clients, but the 75/25% is happening in all of the modes if an entire cart tries connecting at the same time.

I am going to create a new AP group and and assign a middle school wing to it that is wide open and see if they have the same problem. Also, I should probably have the wifi on it's own VLAN/subnet correct? I had planned on doing this to help ease broadcast traffic on the wireless network.
Aruba Employee
Posts: 455
Registered: ‎04-02-2007

Re: WPA2-AES-PSK connectivity/dhcp problems

I would build a separate AP group for each site, and a separate VLAN for each site. They may use the same profiles and configuration, but you'll want to be able to make changes to the VLANs etc. I had assumed the VLAN was big enough, but are you sure you're not running out of leases in this design? If you have plenty of leases you should probably go ahead and give TAC a call for further troubleshooting. I would have though it was a client issue, but if you're having the issue across multiple client types I would give them a call.

The slow down can be other things. G clients for instance will never see the same speed as N clients, and if you're running anything but open or AES you won't get full N speeds per the standard.

-awl
Andy Logan, ACDX
Director, Strategic Account Solutions
Aruba Networks
MVP
Posts: 1,310
Registered: ‎11-07-2008

Re: WPA2-AES-PSK connectivity/dhcp problems

May also check that the max clients per AP isn't set too low, and enable band-steering to get some of the A-capable clients off onto the 5Ghz side and off the 2.4. It sounds like IP lease issues though, being able to re-set the NICs will force a re-arp for an IP and may flush a stale entry out of the DHCP server. Check the available leases OR maybe set DHCP lease timers a lot lower. Bigger VLANs would be better though, just in case...never hurts to wear a belt and suspenders.
Jerrod Howard
Sr. Techical Marketing Engineer
Occasional Contributor II
Posts: 12
Registered: ‎07-07-2011

Re: WPA2-AES-PSK connectivity/dhcp problems




- Max users per AP is 64 and we haven't even had that many users on at once yet this year.
- The subnet is a /16 so there are plenty of IP addresses. Our total devices for the entire district is only in the 1200-1300 range.
- DHCP lease time is set to 4 days right now.

Those should all be fine right?

Occasional Contributor II
Posts: 12
Registered: ‎07-07-2011

Re: WPA2-AES-PSK connectivity/dhcp problems

Our 7th grade wing called this morning and said that none of the computers would connect. These are the Lenovo's with 802.11 capability. When we checked several, they would try connecting, search for an IP for about 5 seconds and then keep repeating that cycle. As soon as we power cycled the access points, they connected and got an IP fine.

I guess we'll see how long that lasts.
Aruba Employee
Posts: 99
Registered: ‎09-08-2010

Re: WPA2-AES-PSK connectivity/dhcp problems

Are the APs on the carts along with the laptops. or are the APs permanently mounted as infrastructure within the building?
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