Cisco APs Ignoring DHCP Option 43 and Using CAPWAP UDP Broadcasts

I cannot tell you exactly what is happening without looking at the configs of the Switches and the WLC you have as I can think of a number of possibilities. For me, it'd be helpful to have that information but more so, the things that you've done. Basically, what are the items you've tried thus far?

SW-A: 10.133.55.1 <---TRUNK---> SW-B: 10.133.55.2

WLC-4404 10.128.55.10

First thoughts though are as follows:

1.) Who is able to ping the WLC? a.) no one = check the interface on the switch and the WLC interface config, any firewalls b.) same subnet, 10.128.55.0/24, but no other subnets = check routing c.) all subnets on one switch but not from another switch = check trunk on SW-A & SW-B

2.) AP and WLC are able to ping each other but AP not showing up in WLC a.) check DHCP has the proper option 43 (Vendor Specific Info) set which tells the AP what IP the WLC is. b.) check any firewalls inbetween c.) create new interface on WLC with the same VLAN subnet as the AP and test d.) enable ssh on the AP and do a show log to see if anything peculiar sticks out

3.) You've checked all possibilities and as the config stands everything should work a.) reload the switches, AP's, WLC b.) pull out the configuration and put the configuration back in specific to the issue c.) try a different interface on the switch for the WLC d.) try a different interface on the WLC (maybe create a new one) e.) get on Cisco.com and use the bugtoolkit to see what bugs are out there for your particular WLC version. f.) upgrade the WLC version a revision up and test.

I realize that some of my ideas are not really applicable, but I'm just throwing some ideas out there to maybe help give a new perspective on the problem. I've found just taking a break to think about something else and then coming back helps me.

I would like to setup some sort of staging/prep area for pre-configuring the new access points, conducting inventory, tagging with asset tags, sorting AP by final deployment area, and so on.

In setting up this staging area, is there a better way to prime these AP's quickly and easily? Or are we already doing this in the most efficient manner?

NOTE: I am assuming you're already familiar with loading MIBs on a Windows / Linux machine, and using snmpwalk / snmpset... if not, please let me know

I recently discovered how well you can manage Cisco's LWAPs through the AIRESPACE-WIRELESS-MIB, in fact I have mostly forsaken our WCS in favor of managing our LWAPs with the MIB (we have a couple hundred LWAPs spread across multiple WLCs at our facility).

Since you know Perl, you could write a loop to poll your WLCs for the new LWAPs; then the script reacts accordingly when it sees a new LWAP mac-address on a WLC.

• Loop through a list of all controllers, then poll the LWAPs on each controller with bsnAPEthernetMacAddress (ro). Use the mac-address as the unique identifying key for all activity on this LWAP.
• When you see a new LWAP, print the discovery time / mac-address of the LWAP; then ask the user what hostname / location to assign to this LWAP

• Optionally perform bsnAPClearConfig (rw) using snmpset (note 255.254.253.252.251.250 is the hexidecimal index to bsnAPTable translated into decimal octets); setting bsnAPClearConfig will immediately reboot the LWAP:

  snmpset -v 2c -OXsq -c private -m AIRESPACE-WIRELESS-MIB <WLC_IP> \
    bsnAPClearConfig.255.254.253.252.251.250 integer 1
  

• Assign bsnAPName (rw), bsnAPPrimaryMwarName (rw), bsnAPSecondaryMwarName (rw) using snmpset

• Get the bsnAPSerialNumber (ro); save it to a CSV file along with bsnAPEthernetMacAddress (ro), bsnAPName (rw), bsnAPPrimaryMwarName (rw), and bsnAPSecondaryMwarName (rw)
• Reset the LWAP if required with bsnAPReset (rw)

Using SNMP to manage LWAPs has been helpful, since I can automatically react to changes in LWAP to WLC mappings, as well as when an AP drops offline or gets large error / user counts. I usually poll them all every 15 minutes and record who is on them, as well as recording what LWAPs are on each controller. The WLC is powerful, but I like building custom-reaction scripts and reports.