DHCP options 60 & 43 on 6509 for Cisco access points

Unanswered Question
Mar 22nd, 2010

I bought Deploying and Troubleshooting Cisco Wireless LAN controllers last month and I'm reading it.  On page 52 it states that I have to configure option 60 in my DHCP scope in order for my scope to deliver option 43 to the access point in order for it to be able to find the controller.  It also states that one DHCP scope can only support one access point type.

I have my scopes built and they work flawlessly without option 60.  I have scopes all similar to this:

=========================================================

ip dhcp pool AP_VLAN

  network 10.127.103.0 255.255.255.0

  default-router 10.127.103.254

  dns-server 10.10.10.10 (name changed to protect the innocent)

  domain-name cisco.com

  option 43 hex f140.0a81.ff0b.0a81.ff0c.(this list goes on for a total of 16 controllers)

==========================================================

None of my controllers are on the 10.127.0.0 network, so they need the option to find the controllers.  I have Cisco 1142s, 1252s, 1240s and 1230s on these DHCP scopes/segments, and they all work just fine. - without any DHCP option 60 set anywhere.

Can anyone explain this for me?

Thanks!

I have this problem too.
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dancampb Mon, 03/22/2010 - 11:12

The reason for option 60 is that when configured option 43 will only be sent to the devices that match option 60.  So if you have 1242's and 1130's and you don't want the 1130's getting option 43 you would make sure option 60 is setup for the 1242's.  If you don't define option 60 then option 43 is provided in every DHCP offer.

tdennehy Mon, 03/22/2010 - 13:54

Dancampb,

Maybe you should have helped out with the writing of this book!  Thank you...  That should have been in the book - the way the book is written it makes you think the option 60 is required, however I know it is not since it works for me without it...

Leo Laohoo Mon, 03/22/2010 - 14:27

I've observed that the 6.X firmware is very much different to the previous 4.X and 5.X in regards to LAPs looking for the WLC.  I never configure the DHCP options because the servers guys in our organizations want a business case.  So I had to resort to "priming" the LAPs prior to deployment.  This works around 80-90% of the cases.  Then came the 6.X firmware.  No priming needed.  The LAPs in different VLANs and subnet seem to be able to just find it.  I have not been able to test this over a WAN link though.

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