Limited or No Connectivity issue with CISCO 1200 Access Points

Hi
We are a school having multiple wireless access point installed. We have three CISCO 1200 wireless access point installed across the long corridor. All APs use same SSID and Channel 11.

 We have 30 Dell Vostro 1520Laptops and I am having trouble with laptops not getting IP addresses and ended up with ‘Limited or No Connectivity’ error message’. Once Laptops get this error message it will take long time to renew the IP address.
This problem is very random when laptop get ip address it will work for good 15-20 minutes and then they will start looking for the IP addresses.

 Event Viewer shows Event ID 1003: Your computer was not able to renew its ip address from the network (from the DHCP server) for the network Card with Network Address.

Event ID 1007: Your Computer has automatically configured the IP address for the Network Card with network address. The IP address is being used is 169.254.139.151

I have used network cable when I get this error message and it connects perfectly using network cable.

I have taken following steps to resolve the issue but no luck

1. Restarting the Laptops, IPconfig/ Renew and Release when they can not get IP addresses
2. I have re-imaged all the laptop with ghost to avoid same SID issue and duplicate DNS records.
3. We have access points above the ceiling and I have tried having antenna upwards and sideways.
4. Deleting DNS records from DNS server.
5. Uninstalled Dell wireless utility and currently using only Windows Wireless Utility.
6. I have used nets tumbler to determine signal Strength and Noise level. I am not too sure how the graph works on it but the average Signal Strength is -50db and Noise level is -100db.
Let me know what else can be done to resolve this issue.

Jatin
ourladysAsked:
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The_RockerCommented:
Are there enough free IP addresses in the pool on your DHCP server?
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ourladysAuthor Commented:
Yes, All three APs have been given fixed IP addresses.
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rxhangoCommented:
You have to change the channels of the Access Points because they interfere with each other.
Is the same thing like three people are speaking loudly at the same time and the fourth cannot understand anyone.
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ourladysAuthor Commented:
I have changed the frequency as per CISCO's manual to 1,6 and 11. but still having the same issue. Limited or No Connectivity message comes up again, after around 10 minutes tried to connect again it connected successfully.
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rxhangoCommented:
How Does it work when you configure laptops with Fixed IP Address
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ourladysAuthor Commented:
I have tried couple of laptop with fix IP addresses and they seem to be working ok. But we want all laptops to get IP from DHCP server and not to use static IP.

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mick442Commented:
Is the DHCP server in the same subnet as the laptops?

What are you using as your DHCP server?

What are the DHCP lease settings on the server?
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rxhangoCommented:
At the time when laptops say Limited or No Network Connectivity, Can they repair their Network Conectivity and fetch The IP from DHCP Server.
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ourladysAuthor Commented:
Repairing Network Connection have no effect, It tries to look for the IP address and comes back with the No Connectivity message.
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rxhangoCommented:
It seems that Cisco aironet 1200 can act as DHCP Servers. Please check the setting of your Access Points to see if this feature is enabled.  The problem is that your bootp requests from Clients dos not pass the Access point from time to time.
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ourladysAuthor Commented:
It can act as DHCP server and give out IP addresses, but I am not sure on how to configure CISCO 1200 as a DHCP server.

I have done some research,  it will requires CISCO IOS tool to configure AP as a DHCP server and this has to be done using Command Line Interface. I am not familiar with this tool and I am sure this can not be done using Web Interface.

Could you give me some instruction on how CLI can be used to configure AP to act as a DHCP server?

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rxhangoCommented:
It is  better you do  not configure your ap as dhcp server if you have another dhcp server.
Follow the guide below in order to allow the ap to forward the dhcp requests to your dhcp server.

http://www.cisco.com/en/US/docs/wireless/access_point/1200/vxworks/configuration/guide/bkscgc7.html#wp1026402
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rxhangoCommented:
The sintax of configuring DHCP Embeded server on AP is:

ip dhcp pool <pool name>

network <IP Network> <Netmask>

default-router <Default router>

dns-server <DNS Server>


Where:
<pool name> is the name of the DHCP pool, such as AP1240
<IP Network> is the network IP address where the controller resides, such as 10.0.15.1
<Netmask> is the subnet mask, such as 255.255.255.0
<Default router> is the IP address of the default router, such as 10.0.0.1
<DNS Server> is the IP address of the DNS server, such as 10.0.10.2



You can find more in here

http://cisco.biz/en/US/docs/wireless/access_point/1250/installation/guide/125h_f.html#wp1007856
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ourladysAuthor Commented:
This documents is for VXworks, we are using software version 12.3(8)JEB.
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rxhangoCommented:
Ok try to configure DHCP configuration on AP but remove the DHCP Server you have
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ourladysAuthor Commented:
Today I had one laptop out of 30 not getting the ip address. I have tried to restart it but could not get IP address.

By giving a static IP address it was connected fine but as soon as I configure it to look for DHCP it failed.
29 other laptops got IP adresses from DHCP and they worked OK

Then I tried to connect to another AP manually which had a different SSID and Channel  and it managed to receive IP address from it. all APs within the school have same configurations. after disconnecting from it and connecting to the original access point it got the IP address.

We would not want to configure our APs to DCHP server if we have to remove the existing DHCP server.
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rxhangoCommented:
So now you have problem with only one Laptop and 29 others are fine???
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ourladysAuthor Commented:
This problem is random sometimes they were all have issues connecting to the network. Today majority of them worked but tomorrow it might not.
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mick442Commented:
what is the topology of the network?  The reason I ask this is because if there is a switch involved and you do not have portfast enabled on the connecting interface, it can cause DHCP issues.
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mick442Commented:
does your AP act as the DHCP server

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rxhangoCommented:
The problems  are caused by wireless connectivity Issues. Make sure you operate on clean frequencies. The best solution will be to add a WLC (Wireless Lan Controller) to your Network. When you have more than one AP you have to face with interference
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yogi59Commented:
ourladys

Make sure that the access points have fixed IPs and are not picking up from the DHCP server, obviously ensuring that they are in the same range as your issued IPs for your laptops, ensure that your channels are seperated correctly as it appears you have done on chs 1,6, and 11. Are yor APs going back to the same switch?
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ourladysAuthor Commented:
Hi Mick

Our AP does not act as a DHCP server. We have a start network.
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ourladysAuthor Commented:
Hi Yogi59

All Aps have fixed IP addresses. All 3 APs are going back to the same switch. Channels have been set to 1,6, 11.

However We have two more APs at the first floor ( other 3 Aps are at the third floor). One is set to channel 4 and another one is set on channel 13.  they are not going to the same switch.

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yogi59Commented:
Jatin

To clarify your set up you have two APs on the first floor on chs 4 and 13, your new 3 APs on the second floor on chs 1,6 and 11 and further three APs on the third floor channels unknown.
During your RF check using NetStumbler were you able to see not only the three new access points but also the two from the first floor and the three from the third floor?
If you could see them depending on the signal strength being recieved from the older APS they will be having an effect on your new units. Also I noticed thatyou have one AP set on Ch 13, now depending on where you are in the world this may cause an issue, here in Europe we have the capability of using channels 1 through 13, but in the States they only use 1 through 11, because most of our hardware is sourced from th US we have to check and ensure that we have the correct client on the mobile devices that will allow all 13 channels and it is not limited to 11.

It sound as if you have a coverage issue either not enough or co-channel interference, the fact that your devices have been picking up an APIPA address as seen with the 169.254.139.151 address it tends to indicate that the clients are unable to connect to the infrastructure and therefore cannot obtain a DHCP pick-up.

I suggest you use NetStumbler to check the RF environment again this time noting the MAC addresses of the APs that can be seen and determine how much coverage you have in the effected area as well as ensuring that all of your APs are visible to the clients.

Hope that helps

Yogi59
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rxhangoCommented:
What was the Solution ??
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