TAC will likely suggest you install 8.0MR5 interim (8.0.141.46) given you have 2700’s (couple of radio bugs are fixed). DFS is as much art as science and older code isn’t always perfect i.e. I’ve seen newer devices that much older code sees as radar. You can request the code here and see the fixes including a number of DFS-related. https://supportforums.cisco.com/t5/wireless-mobility-blogs/8-0mr5-interim-release-availability/ba-p/3098510
Probably too late, but you may want to consider getting to newer code. If you have x700 series WAPs, it’s strongly recommended to be on at least 8.2. 8.2 and beyond have additional innovation in DFS area among many other improvements. Jeff From: "wireless-lan@listserv.educause.edu" <WIRELESS-LAN@LISTSERV.EDUCAUSE.EDU> on behalf of "Watters, John" <john.watt...@ua.edu> Reply-To: "wireless-lan@listserv.educause.edu" <WIRELESS-LAN@LISTSERV.EDUCAUSE.EDU> Date: Monday, August 28, 2017 at 7:42 AM To: "wireless-lan@listserv.educause.edu" <WIRELESS-LAN@LISTSERV.EDUCAUSE.EDU> Subject: [WIRELESS-LAN] DFS Scans Seem to Have Run Amok We are a Cisco shop running 8510 HA WLCs and a variety of AP including 1142s, 2702s, others in smaller quantities for a current total of 6600+ APs. We are running WLC code 8.0.140.16. This was installed on JAN 4. A couple of months ago we started seeing a lot of DFS scans. This was several months after our last code upgrade. When these scans are done, the users of the 5 GHz radio that is doing the scanning for a clear frequency are all kicked off of their connections. Since the scans lasts for 1 minute & 2 seconds, this is very disruptive to the clients. We do not understand why this behavior has suddenly started all over campus. We are not particularly near an airport. There in one on the other side of town but it does not handle commercial service – private planes only plus an occasional charter for a sporting event. And, the APs that do the most frequent DFS scans are located in interior rooms, often on the ground floor of a multistory building. APs located near windows are rarely affected. This is happening in a lot of buildings, and not just in buildings that may tend to have noise in the 5 GHz range (e.g., an engineering building). Has anyone else seen this problem? And, have you found the cause of this behavior. And, more importantly, a fix for the problem. Following is an example from one AP (BRU-202-E2) showing two DSF scans almost back-to-back (2 sec gap) which lasted 3+ minutes: *Aug 28 04:15:52.930: %DOT11-6-DFS_TRIGGERED: DFS: triggered on frequency 5540 MHz *Aug 28 04:15:53.708: %LINK-6-UPDOWN: Interface Dot11Radio1, changed state to down *Aug 28 04:15:53.710: %LINK-5-CHANGED: Interface Dot11Radio1, changed state to reset *Aug 28 04:15:54.707: %LINEPROTO-5-UPDOWN: Line protocol on Interface Dot11Radio1, changed state to down *Aug 28 04:15:54.739: %LINK-6-UPDOWN: Interface Dot11Radio1, changed state to up *Aug 28 04:15:55.739: %LINEPROTO-5-UPDOWN: Line protocol on Interface Dot11Radio1, changed state to up *Aug 28 04:17:53.253: %DOT11-6-DFS_TRIGGERED: DFS: triggered on frequency 5280 MHz *Aug 28 04:17:54.747: %LINK-6-UPDOWN: Interface Dot11Radio1, changed state to down *Aug 28 04:17:54.750: %LINK-5-CHANGED: Interface Dot11Radio1, changed state to reset *Aug 28 04:17:55.747: %LINEPROTO-5-UPDOWN: Line protocol on Interface Dot11Radio1, changed state to down *Aug 28 04:17:55.773: %DOT11-6-DFS_SCAN_START: DFS: Scanning frequency 5300 MHz for 60 seconds. *Aug 28 04:17:55.774: %LINK-6-UPDOWN: Interface Dot11Radio1, changed state to up *Aug 28 04:17:56.774: %LINEPROTO-5-UPDOWN: Line protocol on Interface Dot11Radio1, changed state to up *Aug 28 04:18:57.382: %DOT11-6-DFS_SCAN_COMPLETE: DFS scan complete on frequency 5300 MHz THANKS. John Watters Network Engineer, Office of Information Technology The University of Alabama<https://www.ua.edu/> A115 Gordon Palmer Hall Box 870346 Tuscaloosa, AL 35487 Phone 205-348-3992<tel:205-348-3992> john.watt...@ua.edu<mailto:john.watt...@ua.edu> [he University of Alabama]<https://www.ua.edu/> ********** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/discuss. ********** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/discuss.
