Lwapp AP and DHCP option 43

Answered Question
Sep 2nd, 2010

Hi,


I have configured option 43 on dhcp server, rebooted 1131 AP, but AP always try to resolve CISCO-LWAPP-CONTROLLER instead of ip provided by dhcp. How can I debug this?


Config on router:


ip dhcp pool seg20

option 43 hex f104.0a0f.64fd


Thanx.

Correct Answer by Stephen Rodriguez about 6 years 5 months ago

A CUWN AP, goes through all methods of discovery.  So it always attempts to use DNS, option 43, L3 broadcast, L2 broadcast.  Once it has discovered, then it will unicast the Join request.


  Normal/Expected Behavior

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Correct Answer
Stephen Rodriguez Fri, 09/03/2010 - 10:53

A CUWN AP, goes through all methods of discovery.  So it always attempts to use DNS, option 43, L3 broadcast, L2 broadcast.  Once it has discovered, then it will unicast the Join request.


  Normal/Expected Behavior

u2taz Fri, 09/03/2010 - 11:29

Hi Stephan,


AP doesn't use option 43 even though it is configured. It is always trying to resolve DNS name. Any suggestions?

George Stefanick Fri, 09/03/2010 - 17:12

You are missing your option 60 ...


Check this link .. If this helps please dont forget to rate the post ...


THANKS



http://www.cisco.com/en/US/docs/wireless/access_point/1130/installation/guide/113h_g.html#wp1008197



Configuring Option 43 for 1100, 1130, 1200, 1240, and 1300 Series Lightweight Access Points

To configure DHCP Option 43 for Cisco Aironet 1100, 1130, 1200, 1240, and 1300 series lightweight access points in the embedded Cisco IOS DHCP server, follow these steps:


Step 1 Enter configuration mode at the Cisco IOS CLI.

Step 2 Create the DHCP pool, including the necessary parameters such as default router and name server. A DHCP scope example is as follows:

ip dhcp pool  
network   
default-router  
dns-server  
Where:
 is the name of the DHCP pool, such as AP1240
 is the network IP address where the controller resides, such as 10.0.15.1
 is the subnet mask, such as 255.255.255.0
 is the IP address of the default router, such as 10.0.0.1
 is the IP address of the DNS server, such as 10.0.10.2

Step 3 Add the option 60 line using the following syntax:

option 60 ascii "VCI string" 

For the VCI string, use the value from Table G-1. The quotation marks must be included.

Step 4 Add the option 43 line using the following syntax:

option 43 hex <hex string> 

The hex string is assembled by concatenating the TLV values shown below:

Type + Length + Value

Type is always f1(hex). Length is the number of controller management IP addresses times 4 in hex. Value is the IP address of the controller listed sequentially in hex.

For example, suppose that there are two controllers with management interface IP addresses, 10.126.126.2 and 10.127.127.2. The type is f1(hex). The length is 2 * 4 = 8 = 08 (hex). The IP addresses translate to 0a7e7e02 and 0a7f7f02. Assembling the string then yields f1080a7e7e020a7f7f02. The resulting Cisco IOS command added to the DHCP scope is listed below:

option 43 hex f1080a7e7e020a7f7f02 
Flavio Boniforti Tue, 04/09/2013 - 09:20

Hello George.


As I'm facing the same task with a Fortigate unit, where I need only to put one single WLC, which would the correct option 43 value be?

The WLC IP is 10.30.2.2, which in Hex is 0A1E0202


Now, looking at your explanation, I'm not finding the "length" in the string you typed into your config...


So, how should mine look like?


Kind regards,

F.

George Stefanick Tue, 04/09/2013 - 09:48

Hi


So are you trying to add a option 43 for an access point ? The link above should have the full strings for most model aps.



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Stephen Rodriguez Tue, 04/09/2013 - 10:02

option 43 hex f104.0a1e.0202


the f104 is the length. f104 means one WLC f108 would be two.



HTH,
Steve

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