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New Member

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

1 ACCEPTED SOLUTION

Accepted Solutions
New Member

AP541N wireless clients sporadically not acquiring dhcps

The setting on the Cisco ESW-540-8P (8 port gigabit switch w/POE) I found that worked for me is:

--> Security --> Traffic Control --> Port Security

By default, all ports are set to "Locked / Limited Dynamic Lock / 3 / Discard / Enable / 60"

I simply edited (click the "edit" button to the right) the ports on which I had my WAPs and unchecked "Lock Interface."

That did the trick for me.

Best of luck - hope it works for you, too!

67 REPLIES
New Member

Re: AP541N wireless clients sporadically not acquiring dhcps

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

New Member

Re: AP541N wireless clients sporadically not acquiring dhcps

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
New Member

Re: AP541N wireless clients sporadically not acquiring dhcps

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

New Member

Re: AP541N wireless clients sporadically not acquiring dhcps

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

New Member

Re: AP541N wireless clients sporadically not acquiring dhcps

Thanks for the tip.  I will give it a try.

Best Regards,

Carmine

New Member

Re: AP541N wireless clients sporadically not acquiring dhcps

Congrats. Thanks for your assistance.

Carmine

New Member

Re: AP541N wireless clients sporadically not acquiring dhcps

You're welcome.

Your post helped me for debug.

Let me know if it works for you too.

Regards

Vincent

New Member

Re: AP541N wireless clients sporadically not acquiring dhcps

Vincent,

I will let you know what happens in a few days.

Thanks,

Carmine

New Member

Re: AP541N wireless clients sporadically not acquiring dhcps

Hi Vicent:

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

Thanks and have a great day!

Carmine

New Member

Re: AP541N wireless clients sporadically not acquiring dhcps

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???

Re: AP541N wireless clients sporadically not acquiring dhcps

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

New Member

Re: AP541N wireless clients sporadically not acquiring dhcps

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

Re: AP541N wireless clients sporadically not acquiring dhcps

UMS,

Sorry for my delay.

Small Business Support Center (SBSC) is the small business TAC that covers your first 90 days phone support for the AP541 and up to 3 years if you purchases the "small business pro" service contract.

They are available based on geography:

https://supportforums.cisco.com/docs/DOC-10444

Re: AP541N wireless clients sporadically not acquiring dhcps

Is anyone eles seeing DHCP stop working with AP541 currently?

Steve

New Member

Re: AP541N wireless clients sporadically not acquiring dhcps

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

Re: AP541N wireless clients sporadically not acquiring dhcps

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

New Member

Re: AP541N wireless clients sporadically not acquiring dhcps

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

Re: AP541N wireless clients sporadically not acquiring dhcps

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.

Re: AP541N wireless clients sporadically not acquiring dhcps

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

New Member

Re: AP541N wireless clients sporadically not acquiring dhcps

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?

New Member

Re: AP541N wireless clients sporadically not acquiring dhcps

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

Re: AP541N wireless clients sporadically not acquiring dhcps

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.

New Member

Re: AP541N wireless clients sporadically not acquiring dhcps

Hi Steve:

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

Have a great day!

Carmine

Re: AP541N wireless clients sporadically not acquiring dhcps

We will come back and post when the FW is officially released.

New Member

Re: AP541N wireless clients sporadically not acquiring dhcps

Thanks man.

Re: AP541N wireless clients sporadically not acquiring dhcps

The latest firmware for the Cisco Small Business Pro Wireless Access Point (AP541N) is now online.  The firmware new firmware version is 1.9.0.

Here is the link to the release notes: http://www.cisco.com/en/US/docs/wireless/access_point/csbap/AP541N/release_notes/78-19182.pdf

New Member

Re: AP541N wireless clients sporadically not acquiring dhcps

Thanks Steven.

Best Regards,

Carmine

New Member

Re: AP541N wireless clients sporadically not acquiring dhcps

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

New Member

Re: AP541N wireless clients sporadically not acquiring dhcps

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

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