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The wireless clients cannot obtain an IP address if the backup WLSM activates

Document

Wed, 12/23/2009 - 11:02
Jun 22nd, 2009
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Core Issue

This example is a scenario for Catalyst 6000 series switches (Cat6k) with the Wireless LAN Services Module (WLSM):

Cat6k1------------------------ Cat6k2

WLSM-1 WLSM-2
| |
| |
----- 3750 Switch----
|
AP
|
Wireless client


Resolution

This problem is documented in Cisco bug ID CSCse30752.

In order to resolve this issue, complete these steps:

  1.  
    Remove the Dynamic Host Configuration Protocol (DHCP) snooping on the tunnel interfaces.

       
  2.  
    Ensure the mobility trust is obtained.

       
  3.  
    On the DHCP server, make sure that it verifies the IP addresses before it assigns them.
       

For example, in a DHCP server in Microsoft Windows 2003, configure it with these steps:

  1. Choose Administrative tools > DHCP server.

  2. Right-click the server name.

  3. Choose properties.

  4. Choose Advanced.

  5. Choose two for the Conflict Detection Attempts.

Now, assume interface tunnel 3 is configured for the access point (AP) on the Cat6K switches and that the AP is in Virtual LAN (VLAN) 3.

This configuration must exist on the Cat6K switches:

Active Cat6K

Interface vlan 3
standby 1 ip .
standby 1 priority 105
standby 1 preempt
standby 1 track tunnel 3 10
!--- Decrements of 10 the priority if tunnel 3 deactivates, and it deactivates if there is a WLSM switch.


Standby Cat6K

Interface vlan 3
standby 1 ip
standby 1 preempt
!--- Preempts the active HSRP role if its priority becomes higher than the neighbor.

With this configuration, when the WLSM on the Active Cat6K fails, the tunnel interface 3 on the Active Cat6K deactivates, which triggers the standby priority for the VLAN 3 on the Active Cat6K to decrement by ten and become 95, which is less than the standby priority on the standby Cat6K, which is 100 by default. This results in the activation of the VLAN 3 on the standby Cat6K and the VLAN 3 on the Active Cat6K goes to standby mode.


Problem Type

Associated but cannot pass any traffic


Products

Wireless LAN Service Module (WLSM)


IP Address Assignment

Dynamic addressing (DHCP)

Loading.
b.julin Wed, 12/23/2009 - 11:02
User Badges:
  • Bronze, 100 points or more

Until the TAC exports it, nobody else can read the bug ID you link.


It would be nice if you could cut and paste some material out of your initial case filings to make a better description of the problem and why each of the above steps are needed in order to work around it.

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