interesting Catalyst AP wireless discovery observation

[andy!doesnt!like!uucp]

Hello Wireless dragons :0)
SDA Fabric Wireless at the site full of C9115 APs (WLC 9800-l-f SW 17.10.1).
APs attached to arbitrary edge node & joined WLC (HA SSO) with use DHCP opt 43 & configured for Fabric wireless services still constantly (every 2 mins) broadcast local VLAN capwap discoveries. what could be reason for this???

[Flavio Miranda]

@andy!doesnt!like!uucp 

 Would be possible that those APs are using more than one dicocery process?

We can see on the print you shared that the discovery type is Static configuration although you mentioned option 43.

Wireless LAN Controller Discovery Methods

There are several options to let the Access Points know of the existance of one WLC in the network:

• DHCP Option 43: This option provides the APs the IPv4 address of the WLC to join. This process is convenient for large deployments in which the APs and the WLC are in different sites.
• DHCP Option 52: This option provides the APs the IPv6 address of the WLC to join. Its usage is convenient in the same scenario as DHCP Option 43.
• DNS Discovery: APs queries the domain name CISCO-CAPWAP-CONTROLLER.localdomain. You must configure your DNS server to resolve either the IPv4 or IPv6 address of the WLC tto join. This option is convenient for deployments in which the WLCs are stored in the same site as the APs.
• Layer 3 Broadcast: The APs automatically send a broadcast message to 255.255.255.255. Any WLC within the same subnet as the AP is expected to respond to this discovery request.
• Static configuration: You can use the capwap ap primary-base <wlc-hostname> <wlc-IP-address> command to configure a static entry for a WLC in the AP.
• Mobility Discovery: If the AP was previously joined to a WLC that was part of a mobility group, the AP also saves a record of the WLCs present in that mobility group.

[andy!doesnt!like!uucp]

Hi Flavio
it's exact the reason of the thread - why would APs keep discovering for static configuration if they were successfully discovered WLC with DHCP Option 43: , joined to WLC, have been configured & started servicing? Something nobody would expect to observe...

[Flavio Miranda]

Wondering If the command capwap ap primary-base <wlc-hostname> <wlc-IP-address> was not entered on the AP manually or via script/template

[andy!doesnt!like!uucp]

those are all SDA fabric APs they all got configured via DNAC/WLC.

from other hand shouldnt above command had triggered unicast discoveries instead of broadcasts?

[Flavio Miranda]

Indeed. I would expect the static discovery to be unicast and not broadcast.

[Rich R]

The thing that instantly caught my attention was: WLC 9800-l-f SW 17.10.1

17.10.1 was a limited support release which is effectively end of life already.  Such releases should only be used in exceptional circumstances to provide early support of new features and should be migrated to an extended support release (eg 17.12) as soon as possible.  Refer to TAC recommended link below - currently 17.12.3 but many of us already using 17.12.4 + SMUs + APSP for a large number of additional bug fixes.

[andy!doesnt!like!uucp]

tnx for sharing your opinion, Rich
do u think 17.10.1 as well affects APs & trigger behaviour like this?

[Rich R]

No idea Andy.  There will be hardly anybody using that code (you might even be the only one) and it will never get any fixes so it's best not to waste time thinking about it too much and plan your move to a properly supported code version.  If you were to open a TAC case about it that's the first thing I'd expect TAC to tell you.