cancel
Showing results for 
Search instead for 
Did you mean: 
cancel
Announcements
Community Live- Understanding How Multicast Works with Cisco
468
Views
0
Helpful
8
Replies

Minimum RSSI for NDP to for APs to forum RF Neighborhood

Hello Everyone,

I have an issue here for a warehouse wireless setup where RRM is not changing the RF Channels in the 5 GHz for the APs ( All are on the default 36 channel except one AP where it automatically changed its channel to 64).  These are a mix of Cisco AP 3800 (3802I and 3802E) mode.

The RRM was able to change the RF Channels in the 2.4 GHz for the same APs (although it took several days for that to complete).

My suspicion in that due to the rough environment inside the warehouse, the APs are hearing each other at a level that doesn't satisfy RRM criteria to operate and coordinate RF parameters for them being:

Now, the second criteria (point)  alone would suffice for me to explain why RRM didn't change RF channels for those APs in the 5 GHz band and it did for 2.4 GHz as the RX neighbour are better in 2.4 GHz comparted to 5GHz  (due to 2.4 GHz is better at covering large areas and penetrating through solid objects). the neighbour list are show below:

For 5 GHz Neighbour list:

AP Name.......................................... ap01
Nearby APs
AP 88:cf:xx:ff:2e:4f slot 1.................. -77 dBm on 64 20MHz (11.250.55.1)
AP 50:xx:b5:11:05:8f slot 1.................. -81 dBm on 36 20MHz (11.250.55.1)
AP 50:xx:b5:a4:e4:8f slot 1.................. -83 dBm on 36 20MHz (11.250.55.1)
AP 50:xx:b5:d9:0b:af slot 1.................. -87 dBm on 36 20MHz (11.250.55.1)
AP 50:xx:b5:e6:ca:6f slot 1.................. -80 dBm on 36 20MHz (11.250.55.1)

AP Name.......................................... ap02
Nearby APs
AP 88:cf:xx:ff:2e:4f slot 1.................. -64 dBm on 64 20MHz (11.250.55.1)
AP 50:xx:b511:05:8f slot 1.................. -75 dBm on 36 20MHz (11.250.55.1)
AP 50:xx:b5:d9:0b:af slot 1.................. -73 dBm on 36 20MHz (11.250.55.1)
AP 50:xx:b5:dc:b9:8f slot 1.................. -83 dBm on 36 20MHz (11.250.55.1)
AP 50:xx:b5:e6:ca:6f slot 1.................. -73 dBm on 36 20MHz (11.250.55.1)

AP Name.......................................... ap03
Nearby APs
AP 50:xx:b511:05:8f slot 1.................. -79 dBm on 36 20MHz (11.250.55.1)
AP 50:xx:b5:a4:e4:8f slot 1.................. -62 dBm on 36 20MHz (11.250.55.1)
AP 50:xx:b5:d9:0b:af slot 1.................. -73 dBm on 36 20MHz (11.250.55.1)
AP 50:xx:b5:dc:b9:8f slot 1.................. -76 dBm on 36 20MHz (11.250.55.1)
AP 50:xx:b5:e6:ca:6f slot 1.................. -69 dBm on 36 20MHz (11.250.55.1)

AP Name.......................................... ap04
Nearby APs
AP 88:cf:xx:ff:2e:4f slot 1.................. -73 dBm on 64 20MHz (11.250.55.1)
AP 50:xx:b5:11:05:8f slot 1.................. -86 dBm on 36 20MHz (11.250.55.1)
AP 50:xx:b5:a4:e4:8f slot 1.................. -73 dBm on 36 20MHz (11.250.55.1)
AP 50:xx:b5:e6:ca:6f slot 1.................. -64 dBm on 36 20MHz (11.250.55.1)

AP Name.......................................... ap05
Nearby APs
AP 88:cf:xx:ff:2e:4f slot 1.................. -72 dBm on 64 20MHz (11.250.55.1)
AP 50:xx:b5:a4:e4:8f slot 1.................. -74 dBm on 36 20MHz (11.250.55.1)
AP 50:xx:b5:d9:0b:af slot 1.................. -61 dBm on 36 20MHz (11.250.55.1)
AP 50:xx:b5:dc:b9:8f slot 1.................. -84 dBm on 36 20MHz (11.250.55.1)

AP Name.......................................... ap06
Nearby APs
AP 88:cf:xx:ff:2e:4f slot 1.................. -80 dBm on 64 20MHz (11.250.55.1)
AP 50:xx:b5:a4:e4:8f slot 1.................. -75 dBm on 36 20MHz (11.250.55.1)
AP 50:xx:b5:dc:b9:8f slot 1.................. -82 dBm on 36 20MHz (11.250.55.1)
AP 50:xx:b5:e6:ca:6f slot 1.................. -86 dBm on 36 20MHz (11.250.55.1)

For 2.4 GHz Neighbour list:

AP Name.......................................... ap01
Nearby APs
AP 88:cf:xx:ff:2e:40 slot 0.................. -68 dBm on 6 20MHz (11.250.55.1) ap03
AP 50:xx:b5:7f:05:80 slot 0.................. -67 dBm on 1 20MHz (11.250.55.1) ap06
AP 50:xx:b5:a4:e4:80 slot 0.................. -73 dBm on 1 20MHz (11.250.55.1) ap02
AP 50:xx:b5:d9:0b:a0 slot 0.................. -82 dBm on 11 20MHz (11.250.55.1) ap04
AP 50:xx:b5:e6:ca:60 slot 0.................. -73 dBm on 1 20MHz (11.250.55.1) ap05

AP Name.......................................... ap02
Nearby APs
AP 88:cf:xx:ff:2e:40 slot 0.................. -55 dBm on 6 20MHz (11.250.55.1) ap03
AP 50:xx:b5:7f:05:80 slot 0.................. -63 dBm on 1 20MHz (11.250.55.1) ap06
AP 50:xx:b5:d9:0b:a0 slot 0.................. -65 dBm on 11 20MHz (11.250.55.1) ap04
AP 50:xx:b5:dc:b9:80 slot 0.................. -66 dBm on 11 20MHz (11.250.55.1) ap01
AP 50:xx:b5:e6:ca:60 slot 0.................. -60 dBm on 1 20MHz (11.250.55.1) ap05

AP Name.......................................... ap03
Nearby APs
AP 50:xx:b5:7f:05:80 slot 0.................. -65 dBm on 1 20MHz (11.250.55.1) ap06
AP 50:xx:b5:a4:e4:80 slot 0.................. -52 dBm on 1 20MHz (11.250.55.1) ap02
AP 50:xx:b5:d9:0b:a0 slot 0.................. -64 dBm on 11 20MHz (11.250.55.1) ap04
AP 50:xx:b5:dc:b9:80 slot 0.................. -65 dBm on 11 20MHz (11.250.55.1) ap01
AP 50:xx:b5:e6:ca:60 slot 0.................. -64 dBm on 1 20MHz (11.250.55.1) ap05

AP Name.......................................... ap04
Nearby APs
AP 88:cf:xx:ff:2e:40 slot 0.................. -63 dBm on 6 20MHz (11.250.55.1) ap03
AP 50:xx:b5:7f:05:80 slot 0.................. -77 dBm on 1 20MHz (11.250.55.1) ap06
AP 50:xx:b5:a4:e4:80 slot 0.................. -65 dBm on 1 20MHz (11.250.55.1) ap02
AP 50:xx:b5:dc:b9:80 slot 0.................. -77 dBm on 11 20MHz (11.250.55.1) ap01
AP 50:xx:b5:e6:ca:60 slot 0.................. -61 dBm on 1 20MHz (11.250.55.1) ap05

AP Name.......................................... ap05
Nearby APs
AP 88:cf:xx:ff:2e:40 slot 0.................. -62 dBm on 6 20MHz (11.250.55.1) ap03
AP 50:xx:b5:7f:05:80 slot 0.................. -69 dBm on 1 20MHz (11.250.55.1) ap06
AP 50:xx:b5:a4:e4:80 slot 0.................. -61 dBm on 1 20MHz (11.250.55.1) ap02
AP 50:xx:b5:d9:0b:a0 slot 0.................. -61 dBm on 11 20MHz (11.250.55.1) ap04
AP 50:xx:b5:dc:b9:80 slot 0.................. -69 dBm on 11 20MHz (11.250.55.1) ap01

AP Name.......................................... ap01
Nearby APs
AP 88:cf:xx:ff:2e:40 slot 0.................. -70 dBm on 6 20MHz (11.250.55.1) ap03
AP 50:xx:b5:a4:e4:80 slot 0.................. -64 dBm on 1 20MHz (11.250.55.1) ap02
AP 50:xx:b5:d9:0b:a0 slot 0.................. -77 dBm on 11 20MHz (11.250.55.1) ap04
AP 50:xx:b5:dc:b9:80 slot 0.................. -67 dBm on 11 20MHz (11.250.55.1) ap01
AP 50:xx:b5:e6:ca:60 slot 0.................. -71 dBm on 1 20MHz (11.250.55.1) ap05

 

So are my assumption is correct as above or is it that RRM is working but because the DCA sensitivity in 5GHz is set to medium (15 dBm) and maybe that is not sufficient for the channel change in 5 GHz given those low RSSI NDP values.

Another weird issue I found while debugging RRM event on those 3800 APs (debug rrm neighbor rx & debug rrm neighbor tx) is that all of those AP (total 6) are transmitting NDP packet for the non-DFS channels and channel 64 (one of the AP are operating now on 64) but not for other DFS channels.

So all those APs, NDP Tx are as follow (Summarized from debugging):

Skipping NDP for DFS:

NDP Tx: Channel [Srv:Tx]=[ 36:136] TxPower [Srv:Tx]=[ 10: 23]
wcp/rrm_userspace_1/rrm_schedule :: RRMSchedule rrm_ndp_notify_handler Notification for Request id: 109581622, slot: 1, status 4
wcp/rrm_userspace_1/rrm_schedule :: RRMSchedule write_offchannel_ndp file: /click/cwx1/rrm_receive/offchannel_ndp value: 4 136
wcp/rrm_userspace_1/rrm_schedule :: RRMSchedule rrm_ndp_notify_handler Notification for Request id: 109581622, slot: 1, status 9
Neighbor packet skipped on DFS channel 136

This same Debug message is repeated for all the blow channels:

Neighbor packet skipped on DFS channel 56
Neighbor packet skipped on DFS channel 100
Neighbor packet skipped on DFS channel 132
Neighbor packet skipped on DFS channel 116
Neighbor packet skipped on DFS channel 112
Neighbor packet skipped on DFS channel 136
Neighbor packet skipped on DFS channel 140
Neighbor packet skipped on DFS channel 104
Neighbor packet skipped on DFS channel 52
Neighbor packet skipped on DFS channel 108
Neighbor packet skipped on DFS channel 60

Successful NDP:

NDP Tx: Channel [Srv:Tx]=[ 36: 40] TxPower [Srv:Tx]=[ 10: 16]
wcp/rrm_userspace_1/rrm_schedule :: RRMSchedule rrm_ndp_notify_handler Notification for Request id: 103285576, slot: 1, status 4
wcp/rrm_userspace_1/rrm_schedule :: RRMSchedule write_offchannel_ndp file: /click/cwx1/rrm_receive/offchannel_ndp value: 4 40
wcp/rrm_userspace_1/rrm_schedule :: RRMSchedule rrm_ndp_notify_handler Notification for Request id: 103285576, slot: 1, status 1
Neighbor packet sent successfully on 40

This same Debug message is repeated for all the blow channels:

Neighbor packet sent successfully on 36
Neighbor packet sent successfully on 40
Neighbor packet sent successfully on 44
Neighbor packet sent successfully on 48
Neighbor packet sent successfully on 64
Neighbor packet sent successfully on 1
Neighbor packet sent successfully on 6
Neighbor packet sent successfully on 11

Digging why the APs might skip sending on those DFS channels and found that from RRM white paper "In
order for us to transmit NDP on a channel in the DFS bands that we are not the Master of, we need to first
hear either a Beacon or a directed Probe from a client in order to mark that channel as clear, then we can
follow up with a transmitted NDP packet within 5 seconds. If there are no other AP's, and there are no clients
on other DFS channels, we will never send an NDP on any DFS channel except the one on which we are the
Master."

https://www.cisco.com/c/en/us/td/docs/wireless/controller/technotes/8-3/b_RRM_White_Paper.html

So this section means that NDP would not be sent unless we are the master AP or hear client probing  but even if that is true why some of the AP didn't change channel to one of the non-DFS channels (40,44 and 48) as NDP is successfully being sent and received as confirmed from debugging RRM all AP.

Also all those AP was operating at MAX power until I modified the power threshold, antenna Gain and RXSOP and now they are having mix of power level 2 and 3 (means TPC is working)

WLC Code is 8.2.170.0

 

Sorry for the long post  :) .Any insights !!!!

 

 

8 REPLIES 8
Rising star

Re: Minimum RSSI for NDP to for APs to forum RF Neighborhood

Are you running an RF profile for this site. If so what are the configured settings for it particularly the 5GHz

What RXSOP settings have you configured.

*****Help out other by using the rating system and marking answered questions as "Answered"*****
*** Please rate helpful posts ***
Highlighted

Re: Minimum RSSI for NDP to for APs to forum RF Neighborhood

Thanks for your reply, Yes they are in an RF Profile with these settings 

RF Profile 5GHz RRM.png

RF Profile 5GHz High Density.png

Please note that the Power threshold was at default of -70 dBm but changed to -75 dBm but didn't help and now it is -80 dBm which did help only to lower down the Tx power of the APs

ap04 xx:xx:xx:xx:xx:xx 1 ENABLED UP 36* *3/6 (10 dBm)
ap03 xx:xx:xx:xx:xx:xx 1 ENABLED UP 64* *3/6 (10 dBm)
ap05 xx:xx:xx:xx:xx:xx 1 ENABLED UP 36* *3/6 (10 dBm)
ap01 xx:xx:xx:xx:xx:xx 1 ENABLED UP 36* *2/6 (14 dBm)
ap06 xx:xx:xx:xx:xx:xx 1 ENABLED UP 36* *3/6 (11 dBm)
ap02 xx:xx:xx:xx:xx:xx 1 ENABLED UP 36* *2/6 (13 dBm)

 

RXSOP was set to Medium but I set it to low

 

Hall of Fame Community Legend

Re: Minimum RSSI for NDP to for APs to forum RF Neighborhood

Under DCA, what channels are allowed?

Re: Minimum RSSI for NDP to for APs to forum RF Neighborhood

Hi Leo,

Thanks for your reply. the channels allowed are 36, 40, 44, 48, 52, 56, 60, 64, 100, 104, 108, 112, 116, 132, 136, 140 (Band A and Band B (E-Regulatory Domain)).  the same is allowed globally and under the RF profile for those APs.

BTW, DCA runs each 24 hours 

RF Profile 5GHz RRM.png

Hall of Fame Community Legend

Re: Minimum RSSI for NDP to for APs to forum RF Neighborhood

What is the Regulatory Domain of the APs and what country code are enabled on the WLC?

Re: Minimum RSSI for NDP to for APs to forum RF Neighborhood

-E Regulatory Domain (AIR-AP3802E-E-K9 & AIR-AP3802I-E-K9 ) with the WLC configured with UK as country Code as all of AP and WLC are operating in the UK

VIP Advocate

Re: Minimum RSSI for NDP to for APs to forum RF Neighborhood

Based on your previous output, your APs are hearing each other with just a fairly weak signal (less than -70 dBi). So everything is actually working as intended, as you already found out in your first post.
In the general 802.11a/n/ac DCA properties make sure that "Avoid Cisco AP load" is enabled. In case you do have a somewhat high load on the APs, they would switch the channel at the next DCA run. Of course, if you run DCA only once in the night, when nobody is working, then the APs will never switch the channel.
Hall of Fame Community Legend

Re: Minimum RSSI for NDP to for APs to forum RF Neighborhood

I'm with Patrick.
It looks like the DCA and RRM are operating normally.
CreatePlease to create content
Content for Community-Ad
August's Community Spotlight Awards