AP541N wireless clients sporadically not acquiring dhcps

Unanswered Question
Feb 26th, 2010

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

I have this problem too.
0 votes
  • 1
  • 2
  • 3
  • 4
  • 5
Average Rating: 0 (0 ratings)
cascoli_2008 Fri, 02/26/2010 - 09:25

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.htm Use 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 our suggestions would be greatly appreciated!

Sincerely,

Carmine

UMS-Orsay Thu, 03/04/2010 - 03:20

Hi,

We are experiencing the same kind of problem.

Our config :

2 clustered APs :

  • AP1 fixed on channel 1
  • AP2 fixed on channel 6

3 SSIDs :

  • 1 on VLAN 1 (untagged) dedicated to internal standard communication
  • 1 on VLAN 5 (tagged) dedicated to guests - direct acces to internet
  • 1 on VLAN 1 (untagged) dedicated to some thermo/hygro probes

on VLAN 1, a W2K3 server acts as DHCP server

on VLAN 5, a small NetGear routeur acts as DHCP server

The problem :

After an irregular period after rebooting the AP or putting off/on the radio interface (from couple of hours to ~2 days) we can see the following :

  • DHCP on AP1 / VLAN 1 stops responding (the dhcp offers are not retransmitted from the LAN side of the AP to the WLAN side...verified with WireShark)
  • DHCP on AP1 / VLAN 5 is still responding correctly
  • DHCP on AP2 / VLAN 1 & 5 are still responding correctly
  • SNMP Communications from the wired LAN to the thermo/hygro probes on AP1 / VLAN 1 stops working
  • SNMP Communications from the thermo/hygro probes on AP1 / VLAN 1 to the wired LAN still works properly
  • Through the Web Access Point Config Utility > Cluster > Session, we can observe a rising error rate on most of active sessions but no Dropped Packets are recorded on the Status > Associated clients page...

Other remarks :

When this appends, configuring a static IP address for a client connected to AP1 / VLAN 1 allows it to reach any LAN ressources succesfully.

Switching the APs (AP1 in place of AP2 and vice-versa) just switches the problem from AP1 to AP2 that's why we first thought about radio perturbations, but what kind of radio perturbations could cause some particular protocols, only from the lan to the wlan, and for all SSIDs linked to a particular VLAN to fail ?

So... any ideas ?

Regards,

Vincent

PS :

  • Most of our laptops are Dell too (D400 & D600 series) but setting the emitting power to the maximum value did not solve the problem at all.
  • The Firmware of the APs is AP541N-K9-1.8(0) (lastest)
  • Radio mode is 802.11b/g
UMS-Orsay Mon, 03/08/2010 - 00:09

Looks like I've sold one part of the problem !

thermo-hygro probes are now working fine since I've set the Broadcast Key Refresh Rate to 3600 sec for all SSIDs and disabled use of WiFi-Multimedia in QoS Parameters (don't really know which one made it work).

As you got similar issues to mines with a W2K3 DHCP and as my other, may be 'more standard', DHCP does work, I definitely think about a compatibility problem with the MS DHCP server.

I'm now trying to configure the W2K3 DHCP server to annonce just like the other one (if possible).

I'll let you know if I find the correct parameters.

Regards

Vincent

UMS-Orsay Mon, 03/08/2010 - 02:59

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.

Regards

Vincent

UMS-Orsay Mon, 03/08/2010 - 05:12

You're welcome.

Your post helped me for debug.

Let me know if it works for you too.

Regards

Vincent

cascoli_2008 Mon, 03/22/2010 - 07:20

Hi Vicent:

Your fix (registry hack to my win2k3 dhcp server) has seemed to resolve my issue.

Thanks and have a great day!

Carmine

amcsolutions Sat, 03/20/2010 - 15:55

We got 4 of these, I have one at my home office for testing and have to reboot it frequently to get an IP address from a Sonicwall firewall that is handing out DHCP.

Have another one at a client site that was OK being a guinea pig at first, but their patience has worn out. They have to reboot every at least once a day, but sometimes 5-6 times a day with the same issue - all of the sudden they can't get DHCP and even the devices with a static address won't connect any longer.

The customers say that they had less problems with their $50 DLink and want to put that one back in....that's embarrassing.  Cisco Small Business Support is telling us to upgrade our Wireless Network Card Drivers on every device that connects as a fix, but it seems odd that we have the same problem in different environments with several different wireless NICs - and it appears most others are having the same problem according to this forum.

Where you at Cisco Engineers???

Steven DiStefano Sat, 03/20/2010 - 15:59

I saw this topic last week, and I sent it direct to the PM in Cisco (Brian N), who may have been out of the office.

But this is not good, and I suggest a SBSC case be opened ASAP and they can escalate alot better than this community, which is RSS feed and email based.

Steve

SE

UMS-Orsay Sat, 03/20/2010 - 17:21

Great

At last some "real" help ^^

But what do you mean by "I suggest a SBSC case be opened ASAP" ?

Must we open it by ourselves (and if yes, what exactly is a SBSC and how to open one ?) or will this be done by your side ?

Anyway I suggest you take a look a this topic too : https://www.myciscocommunity.com/message/40534#40534

To my mind, theese two are linked together.

Regards

Vincent

cascoli_2008 Mon, 03/22/2010 - 14:20

Steve,

I did before following Vicent's instructions.

The Cisco AP541 access point 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.

Regards
Carmine

Steven DiStefano Mon, 03/22/2010 - 14:28

Hi Carmine,

First, thank you for all you help BTW.   We appreciate it.

... perhaps another way to skin this cat if it happens again...

(some Engineers suggested this to see if it helped and it would tell more about the problem...)

On AP541N GUI on the Wireless Advanced tab.

Disable Broadcast/Multicast Rate Limiting

Rate_limit.GIF

UMS-Orsay Tue, 03/23/2010 - 02:07

Hi Steve

Disabling Broadcast/Multicast Rate Limiting is the default config, and for my part I let this setting as is since the begining (except for a 2 days long test that didn't improved anything).

I'm ok to say that changing the MS DHCP response rules does not resolve the whole issue : It only allows standard DHCP clients (mainly Dell laptops for my part) to connect and communicate trough the AP even when it starts working "degraded mode"... but I still encouter some problem with more "light" clients as Aginova thremo/hygro probes.

Concerning the SBSC, I'm affraid I've no specific contract with Cisco except the fact I bought 2 APs... but It's older thant 90 days...

Would it be usefull to send the equipment's serial number to someone ?

Regards

Vincent

Steven DiStefano Tue, 03/23/2010 - 06:47

If you didnt purchase the 3 year SKU for the product, I am not sure you can buy it on the fly, but you should check with your Small Business Account manager.

Steven DiStefano Tue, 03/23/2010 - 08:49

Sounds like you may be using older firmware, since v1.8.0 has bcast/mcast rate limited ENABLED by default.

Per the help file in v.1.8.0, if you have this firmware version and your multicast is disabled by default you must do a factory default and reconfigure (the config file can get misinterpreted as many default parameters were changed between the two available f/w versions).

Steve

amcsolutions Wed, 03/24/2010 - 19:40

Anybody get anywhere with this?

Although I don't like the idea of a registry fix being required to get an access point to work, I'd gladly oblige and test it out.

Unfortunately, I'm getting DHCP from a Sonicwall firewall.

I've disabled the broadcasting stuff recommended but still have to reboot the access point every couple hours to keep a connection.

Anybody else find a solution, besides returning these devices for other products?

cascoli_2008 Mon, 03/29/2010 - 08:43

One thing I have noticed with Dell laptops using the Dell or Intel wireless utility to manage wireless networks.  If you are trying to use the built-in Microsoft Windows wireless utility to manage your wireless network and you have either the Dell or Intel wireless utility enabled then this can confuse the wireless adapter and prevent it from acquiring a dhcp address.  The best solution is to uninstall it or disable it in services.

Best Regards,

Carmine

Steven DiStefano Wed, 04/07/2010 - 13:32

Tier 2 Support and the BU have communicated to us  that the Level 1 SBSC agents were informed of this AP541N issue and another "Degrading" issue as being solved in  the next FW release for this product.  When customers call SBSC, the support the agents will follow proper protocol and due  diligence to determine the problem, and in the event it is considered to  be resolved in the coming release, the case will be escalated to 2nd level support.  At that time and at the Partners discretion, access to  the beta firmware 1.9.0 in test right now can be given, once a beta agreement has been accepted.

Any Partner experiencing either DHCP issues or degrading service, please contact the SBSC for further  resolution.

I do  not have an ETA for the formal release of 1.9.0.

Steve DiStefano

Systems  Engineer,

Partner Sales, U.S.

cascoli_2008 Wed, 04/07/2010 - 13:42

Hi Steve:

Thanks for the update.  Can you let me know when the version 1.9 firmware gets released.

Have a great day!

Carmine

cascoli_2008 Mon, 07/05/2010 - 09:39

Hi Steve:

I hope things are going well.  Do you know if Cisco has release any new firmware upgrades since version 1.9.

Thanks,

Carmine

christopheradlam Tue, 07/06/2010 - 09:26

The most recent release is now 1.9.1 for the AP541N. It was released on the 3rd of June.

Release notes through to this release:

http://www.cisco.com/en/US/docs/wireless/access_point/csbap/AP541N/release_notes/78-19182.pdf

The issues listed in this thread should have been fixed in the 1.9.0 release, as per the following two closed caveats in the release notes:

Closed Caveats
The following caveats have been resolved in version 1.9.0:


CSCtg28316—WL Driver Multicast Queue Freezes
After a period of time, the access point stops forwarding Multicast or Broadcast
frames. Also, the last frame on the MCast queue is not always cleared.


CSCtg28338—WPA Key Refresh Freezes
If during disassociation the access point is refreshing a client broadcast key, that
client is not accounted for and the WPA key state machine freezes.

Though the new open caveats for 1.9.1 do prompt some worry:

Open Caveats


CSCtg14132—Station Isolation is Sporadic
Occasionally when Station Isolation (local LAN communication) is set to Disabled
auto, the device reverts to a Blocking state. The configuration continues to
indicate that the feature is Disabled. As a result, computers cannot access local
devices, such as printers. Access to remote devices (outside the local AP LAN)
can be accessed (for example, access to an external Web site).
Workaround: Reboot or restart the device.


CSCtg12675—MAC Filtering Set To Block Fails to Block Access
If you set MAC Filtering to block specified addresses, the device fails to prevent
association and authentication.
Workaround: None

lokibjensen Fri, 02/25/2011 - 12:57

Hi Christopher,

I know that this is an old thread but I was wondering if you have found any more issues with your AP's.  The reason I ask is that we bought 6 of these with firmware version 1.9.0 already installed on it and have since upgraded two times to the current firmware (and performed factory reset) and we are still having issues.  At first, after speaking with support for the fifth time I thought it may be the switch.  I have since replaced the ESW-540 switch with an SG-300 (for free) and am still having the same issues where the clients will all of a sudden not be able to pull DHCP.  It's driving me crazy and the clients are beyond pissed.  Funny though, Cisco Small Business support had never even mentioned that they'd heard of this before and I've created so many cases about it.

Since I found your thread I have disabled the key refreshing on the VAP's, and disabled the Broadcast/Multicast Limit Rating.  I hope that works but I just wanted to see if you or anyone else was still experiencing issues with this.

Please let me know.  Thanks!

DHCP server is from a SonicWALL NSA 240.

cascoli_2008 Fri, 02/25/2011 - 13:25

Hi Christopher:

This sounds like an issue with the DHCP server on the SonicWall.  I would contact those folks.

Best Regards,

Carmine

lokibjensen Fri, 02/25/2011 - 13:28

Nope....the SonicWALL has no problems passing DHCP to the LAN.  It's only through the AP's where the problem comes in.  Also, we had a Cisco 1241 on the same network and have no issues with that.  I had the same issue in another location with the AP541n and a Cisco 871 router.  Finally got rid of that AP but in this location I can't get rid of all the AP's without losing a lot of money. :(

christopheradlam Mon, 03/07/2011 - 09:42

I was having an issue with them dropping clients (different issue) but that was with WPA/TKIP. Moving to WPA2/AES fixed that one (yes, that's a bug for sure!).

I have a few of these in the field with a number of different devices providing DHCP:

1. Cisco 1841

2. IPCop Linux box

3. Cisco 871 (two AP541's behind this one)

And I have not encountered any issues with DHCP. Just the wireless client disconnect issue I mentioned above.

If you set the clients to a static IP when DHCP stops working, can the client function normally?

lokibjensen Mon, 03/07/2011 - 11:38

Thanks for the reply Christopher.  Yes, when I set a static IP the clients perform as expected.  It is only after some time that they will stop getting IP's from DHCP.  Wired clients are completely unaffected.  I have yet another case going with Cisco right now on this one.  Hopefully once and for all we can come up with a solution to this issue.  It has gone on for far too long.  Thanks again!

UMS-Orsay Tue, 03/08/2011 - 03:31

Hi all,

What I'm affraid of is that the lastest firmware (1.9.2) seems to be compliant with V2 hardware only...

And wheareas the release notes for 1.9.1 firmware annonce the problem about broadcast/multicast frames as solved (the one that avoids DHCP from working properly), It has not solved anything for me !

So... will there be some more firmwares for V1 hardware or must we just get rid of those unreliable APs ?

Can we change for free our V1 for V2 harware platforms ?

And first... does V2 hardware works properly ?

To be clear, I've switched my APs from another brand to cisco thinking this would be the end of all my harware problems... but it is worth !

My company will be relocated soon, I'm in charge of choosing the network hardware... I was about to invest in a full cisco solution but what I've experienced with theese test materials really makes me wonder if this is a good choice...

cascoli_2008 Tue, 03/23/2010 - 05:41

Hi Steve.

You are welcome.  I believe Vincent already tried to disbabling the Broadcast/Multicast Rate Limiting and it only worked for certain clients for him.  However, you could try it as an experiment.

Best Regards,

Carmine

streaves Wed, 03/09/2011 - 15:01

AP541N version 1 hardware is the only available hardware and is compatible with all firmware versions up to and including 1.9.2. I've checked with product engineering and there are no reported reliability issues with version 1 hardware. Please stay tuned for version 2.0 firmware to be released in the coming months.

Download firmware version 1.9.2

Release Notes for firmware version 1.9.2

Please contact the Small Business Support Center for persistant issues and thank you for participating in the Community.

Stephanie Reaves

Cisco Small Business Technology Group

UMS-Orsay Thu, 03/10/2011 - 03:24

Hi Stephanie,

Thanks for your response but...

- the link you provide for 1.9.2 firmare release notes seems broken... I got the following message :

"The file or application you are trying to access may require additional entitlement or you are trying to access a file with an invalid name. Additional entitlement levels are granted based on a users relationship with Cisco on a per-application basis."

- the release notes I could find by myself ( http://www.cisco.com/en/US/docs/wireless/access_point/csbap/AP541N/release_notes/78-19182.pdf ) says :

"Devices with hardware version ID (VID) V02 only support firmware version 1.9.2"

I agree to say that this doesn't mean that V01 platforms does not support 1.9.2 firmware (as this point was not really clear I didn't take risks... furthermore, release notes says that this version doesn't close any additional caveats as compared to the 1.9.1...) but to my mind it tends to proof the existence of V02 platform... so where is the truth ?

I've recently invested in a Cisco Small Business RVS 4000 router thinking it would be fully compatible with my four AP541N (all under 1.9.1 firmware) witch would at last relay DHCP frames as required but I still got the problem... So be sure I'll stay tuned for version 2.0 firmware !

Regards

Vincent

streaves Thu, 03/10/2011 - 09:54

Hi Vincent --

Couple of different things here:

AP541N firmware does not require any kind of login. Likely a cookie issue. Clear your cache and cookies, open a new browser and try download again, please.

V2 hardware is not available but can definitely see how the Release Notes are misleading. Product Management is taking steps to clarify the Release Notes now. Sincere thanks for pointing this out to us.

Please send me email (streaves at cisco dot com) so I can share a couple of other options.

Thanks,

Stephanie Reaves

Cisco Small Business

hedesk Wed, 03/16/2011 - 11:38

Hi Vincent and Stephanie

     I can confirm that my site is seeing this issue as well.  We have tested with Dell Notebooks, Apple iPhones (3GS and 4), Apple iPad, and BlackBerry devices.  Network caputure traces show that the DHCP Client never recieves the DHCP ACK from the server and thus does not acquire an IP address.

The only resolution for this at the moment is to restart the AP541N.  This issue has been verified under firmwares 1.8.0, 1.9.1 and 1.9.2. 

Reguards

Shaun

rmanthey Wed, 03/16/2011 - 15:29

Currently the DHCP ACK issue was resolved with firmware 1.9.2. If you are still having a similar issue please call in to Cisco Small Business Support so we can properly troubleshoot the issue. Please have a detailed Network topology, including Channels used Number of AP's, What is giving DHCP out, number of SSID's and Vlans. If you have traffic monitoring tools this will also help the TAC engineer in finding the root cause, or being able to diagnose a bug. Currently though no bug for DHCP is known by Cisco for the AP541N running firmware 1.9.2.

Thanks,

Randy Manthey

Cisco Small Business Support

hlmhlw-krems Thu, 03/17/2011 - 04:44

We have 17 AP541N (FW 1.9.2) and we have the same problems. Sometimes - after 3 hours to a day - some of the AP stop working properly. The WLAN-clients are connected to the AP but they get no IP from the MS DHCP server. We have no issues on clients which are connected via wired LAN. Only a reboot of the AP solves the problem and then the WLAN-clients get an IP. We decided to buy Cisco-APs because we thought Cisco products do not perform such issues...

Regards, Mario

lokibjensen Fri, 03/18/2011 - 06:15

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.

rmanthey Fri, 03/18/2011 - 06:55

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

hlmhlw-krems Mon, 03/21/2011 - 09:15

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

streaves Mon, 03/21/2011 - 09:29

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

cascoli_2008 Mon, 03/21/2011 - 09:33

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

hlmhlw-krems Tue, 03/29/2011 - 03:43

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

Actions

Login or Register to take actions

This Discussion

Posted February 26, 2010 at 8:35 AM
Stats:
Replies:65 Avg. Rating:
Views:16849 Votes:0
Shares:0
Tags: No tags.

Discussions Leaderboard