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AP541N wireless clients sporadically not acquiring dhcps

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AP541N wireless clients sporadically not acquiring dhcps

Postby Guest » Mon Nov 09, 2009 7:33 pm

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

Guest
 

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Re:AP541N wireless clients sporadically not acquiring dhcps

Postby Guest » Mon Nov 09, 2009 9:13 pm

AP541N wireless clients sporadically not acquiring dhcps

Guest
 

Re:AP541N wireless clients sporadically not acquiring dhcps

Postby Guest » Mon Nov 09, 2009 10:08 pm

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 thats 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
Guest
 

Re:AP541N wireless clients sporadically not acquiring dhcps

Postby Guest » Mon Nov 09, 2009 11:26 pm

Looks like Ive sold one part of the problem !

 

thermo-hygro probes are now working fine since Ive set the Broadcast Key Refresh Rate to 3600 sec for all SSIDs and disabled use of WiFi-Multimedia in QoS Parameters (don 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.

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

 

Ill let you know if I find the correct parameters.

 

Regards

Vincent

Guest
 

Re:AP541N wireless clients sporadically not acquiring dhcps

Postby Guest » Mon Nov 09, 2009 11:49 pm

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 servers hive :

HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesDHCPServerParametersIgnoreBroadcastFlag

and set its 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 its radio interface, causes the clients to aquire immediatly an IP address from the W2K3 DHCP server.

 

Regards

Vincent

Guest
 



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