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cascoli_2008
Beginner

AP541N wireless clients sporadically not acquiring dhcps

I was having this issue with my Dell Precision M70 laptop until I made this tweak to the Intel Pro Wireless 2200BG card that is built-in and so far its seems to be making a difference with it connecting to our Cisco 541L APs and acquiring a DHCP from our network.  However, the only thing different I noticed after making this change is that it is initially a bit slow at connecting to the Cisco APs.

http://www.intel.com/support/wireless/wlan/sb/cs-006205.htmUse Intel® PROSet/Wireless WiFi Connection Utility to Set CAM1.     Click Advanced > Adapter Settings > Advanced tab. 2.     Select Power Management and uncheck Default / Auto and move the slider to Highest / Maximum Performance.If the slider is already at Highest / Maximum Performance, move the slider to another setting and then back to Highest / Maximum Performance.


We are still experiencing this issue with our Dell Latitude E4200 laptops but need to verify that they are using the latest wireless network adapter drivers.  In addition, I am planning to tweak the PSP as I did with the Intel Pro Wireless 2200 BG.

F.Y.I. Our PDC and Primary DNS server is a Windows Server 2000

         Our BDC, Secondary DNS and DHCP server is a Windows Server 2003

Any help or suggestions would be greatly appreciated!

Sincerely,

Carmine

67 REPLIES 67

I'm glad that more people are chiming in with the same problem because for the first few months Cisco support had no idea

what the issue was with our AP's, then for the next few months they told me that I was the only one with the issue.  At least now they know I'm not crazy.

I want to thank everyone for posting on the forum, but we do need to have a case created to assist in diagnosing the problem, so if you are experiencing a similar issue with the AP541N and are on the latest firmware of 1.9.2, please call Cisco Small Business Support.

Thanks,

Cisco Small Business Support Center

Randy Manthey

CCNA, CCNA - Security

Hello Randy,

I've already called Cisco Small Business Support and I got the promise that somebody would call me back. But nothing happened... I am still waiting...

Regards Mario

Hi Mario -- Sorry you weren't contacted. Can you please provide the Small Business Support Center ticket number you were given so we can investigate?

Thanks,

Stephanie Reaves
Cisco Small Business

Hi Stephanie,

See below email. This solution resolved this issue for me.

I got it fixed !

The NetGear router answers to DHCP Discover by an IP unicast DHCP Offer while

the W2K3 DCHP server answers to DHCP Discover by an IP broadcast DHCP Offer !

Reading the following page, you can see this is an MS DHCP feature that causes some known issues with some 3rd party network equipments.

http://blogs.technet.com/teamdhcp/archive/2009/02/12/dhcp-broadcast-flag-handling-in-windows-7.aspx

To avoid this and make the MS DHCP server answer by unicast DHCP Offers, you should create the following DWORD entry into your W2K3 server's hive :

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\DHCPServer\Parameters\IgnoreBroadcastFlag

and set it's value to 0 as explained here : http://technet.microsoft.com/en-us/library/cc958946.aspx

This solved the problem for me : restarting the DHCPServer service after creating this entry, without rebooting the AP nor putting off/on it's radio interface, causes the clients to aquire immediatly an IP address from the W2K3 DHCP server.

https://supportforums.cisco.com/message/3078962#3078962

Best Regards,

Carmine

Carmine Ascoli

IT Systems Administrator

Hi Stephanie,

I am still waiting for the call. Nothing happend until now...

My case number: 617226695

I have called SBSC in Austria. Can you investigate?

Regards Mario

Hi, My name is Eric Moyers. I am a Network Support Engineer in the Cisco Small Business Support Center. Can I get your case number? After getting that from you I can follow-up with the engineer that started your case and get back to you. You can respond here or contact me directly by sending an email to emoyersatciscodotcom

THanks

Eric Moyers
Cisco Network Support Engineer
1-866-606-1866

Hi Eric,

I have no case number for this issue. I resolved it last year through my own research.

Best Regards,

Carmine

Carmine Ascoli

IT Systems Administrator

Thank you for the quick reply. I actually intended this for Mario Lahner up alittle further

in your post who says he was expecting a Callback from us and never got one. Just trying to reach to him and

see how we can help.

Thanks Again, and Thank you for posting on the Community Forums.

Eric Moyers
Cisco Network Support Engineer
1-866-606-1866

Oops! No worries.

Have a great day!

Carmine

Carmine Ascoli

IT Systems Administrator

Mario and lokibjensen,

Did Carmine's fix work for either of you?

I thought it had fixed the problem for me, but I still see the problem (though not as often recently).  After replacing all 3 WAPs via RMA, problem still existed.

Randy - My case number is 616719113.

I have a Sonicwall NSA 3500 providing DHCP on VLAN2 and a MS 2k3 server providin DHCP on VLAN1.  Using a SRW2048 switch.

VLAN2 is for guest internet, VLAN1 is for normal LAN access.

The DHCP issue happens with both the MS DHCP server and Sonicwall.  No issues with wired DHCP requests from either.  Static entries also work fine.  We have HPs, Thinkpads, iPhones, iPads, Droids, and Dells.

Running firmware 1.9(2) on 3 AP541Ns in clustered mode. 

20 MHhz Bandwidth

Broadcast/Multicast Rate Limiting is enabled at 100/150


Recently removed the DHCP Ignorebroadcast registry key, as it didn't seem to make a difference.

I'll see messages like this in the log:

Mar 8 10:08:29  info  hostapd  The wireless client with MAC address xxxxxxxx has been successfully authenticated. 
Mar 8 10:08:29  info  hostapd  wlan0vap3: STA xxxxxxxxxx WPA: pairwise key exchange completed (WPAv2) 
Mar 8 10:08:29  info  hostapd  wlan0vap3: IEEE 802.11 STA xxxxxxxx associated with BSSID yyyyyyyyyy

Mar 8 10:08:29  info  hostapd  wlan0vap3: IEEE 802.11 Assoc request from xxxxxxxx BSSID yyyyyyyyyy SSID PharosWireless@ 
Mar 8 10:08:29  info  hostapd  wlan0vap3: IEEE 802.11 STA xxxxxxxx deauthed from BSSID yyyyyyyyyy reason 3 
Mar 8 10:08:26  info  hostapd  wlan0vap3: IEEE 802.11 STA xxxxxxxx disassociated from BSSID yyyyyyyyyy reason 8

Where is the key for reason 1 - 8?

-Damon

@Damon,

No I can't use the solution as I am using a SonicWALL to give out DHCP and have no Microsoft server at the site.  I am still working with support on this now going on many months but with many different cases.  Unfortunately or fortunately I received a call yesterday about the case but they want me to send all of the information I have already given many times over all over again.  I will gather the info when I have time and send it to them.  I'm just glad that there are other people with the same issue now but unfortunately my clients patience is pretty much over with.  If it fails again I will be out thousands of dollars having to take all of the equipment back.  I have already switched out their switch for free out of my own pocket because previous support attempts led me to believe it was the switch and not the AP's.

Good luck!

Hi Damon,

Carmine's fix does not work for me as I hoped. This issue occurs (3 hours to one week?!) until now. Before I tried Carmine's fix the WLAN clients were not able to get an IP when the AP is affected. With Carmine's fix the clients instantly get an IP but then it is not possible to ping all IP addresses in my network. Some IPs are not pingable. However some are...

When a client is connected to an affected AP and I use static IP addresses everything is working properly and I can ping all IP addresses. When I switch back to DHCP addresses during the client is connected some IPs (mostly different ones) are not reachable. A reboot helps and the AP is working fine. But for how long?

Sometimes I recognize that the data transfer rate also decreases whe the issue occurs.

It seems for me that this issue is associated to the "service degrading" issue which is mentioned in the community. I think it's the same issue...

Randy and Eric: My case number: 617226695

Regards Mario

Can you try using an different DHCP server?

I ask because we have a similar setup (Blackberries, iPhones, iPad... tons of laptops...etc) but we are using a Linux box (IPCop) for DHCP and have not experienced this issue.

Hi Christopher:

I got it fixed !

The NetGear router answers to DHCP Discover by an IP unicast DHCP Offer while

the W2K3 DCHP server answers to DHCP Discover by an IP broadcast DHCP Offer !

Reading the following page, you can see this is an MS DHCP feature that causes some known issues with some 3rd party network equipments.

http://blogs.technet.com/teamdhcp/archive/2009/02/12/dhcp-broadcast-flag-handling-in-windows-7.aspx

To avoid this and make the MS DHCP server answer by unicast DHCP Offers, you should create the following DWORD entry into your W2K3 server's hive :

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\DHCPServer\Parameters\IgnoreBroadcastFlag

and set it's value to 0 as explained here : http://technet.microsoft.com/en-us/library/cc958946.aspx

This solved the problem for me : restarting the DHCPServer service after creating this entry, without rebooting the AP nor putting off/on it's radio interface, causes the clients to aquire immediatly an IP address from the W2K3 DHCP server.

https://supportforums.cisco.com/message/3078962#3078962

Best Regards,

Carmine

Carmine Ascoli

IT Systems Administrator