In this post we will see how to configure RRM on a cisco WLC.
APs send neighbor messages every 60s at max power, at lowest data rate and on all serviced channels to the multicast address of :01:0B:85:00:00:00. These messages contain Radio Identifier, Group ID, WLC IP Address (Group Leader), AP Channel, Neighbor messages Channel, Power, Antenna Pattern.
If a AP receives a neighbor messages and cannot decode or it never receives a neighbor msg from an AP, that AP considered to be a rouge AP. Group Leader is the WLC with highest group leader priority. RRM is per radio band(ie separate groups for 2.4 GHz & 5 GHz) & two WLC can be group leader for these two.
To configure RRM, you would need to given an RF group name for the controller. That’s pretty much it for most of deployments. During Initial Wizard you can configure this & later on change it if you want.
If you want to view or edit RRM configuration per radio band, you can do that via “Wireless ->802.11a/n or 802.11b/g/n -> RRM” section. Here is the 802.11a/n RRM grouping info in one of my controller.
You can change this group mode to static by choosing ” Leader” option in drop down menu. If you want do disable RRM you can select “off” option. By default it is “auto”.
If you select static configuration option (ie Leader option) you can add members into RF group as shown in the below.
In CLI, You can use “show advanced 802.11a group” command to see the status of WLC in RF groupl
(WLC1) >show advanced 802.11a group Radio RF Grouping 802.11a Group Mode............................. AUTO 802.11a Group Update Interval.................. 600 seconds 802.11a Group Leader........................... WLC1 (10.10.111.10) 802.11a Group Member......................... WLC1 (10.10.111.10) 802.11a Group Member......................... WLC2 (10.10.112.10) 802.11a Last Run............................... 182 seconds ago
You can verify this config in CLI mode as well. If you type ” show advanced 802.11a channel” (since we configure RRM group leader for 802.11a) you will see something like this.
(WLC2) >show advanced 802.11a channel Automatic Channel Assignment Channel Assignment Mode........................ AUTO Channel Update Interval........................ 600 seconds [startup] Anchor time (Hour of the day).................. 0 Channel Update Contribution.................... SNI.. CleanAir Event-driven RRM option............... Disabled CleanAir Event-driven RRM sensitivity.......... Medium Channel Assignment Leader...................... WLC2 (10.10.112.10) Last Run....................................... 495 seconds ago DCA Sensitivity Level.......................... STARTUP (5 dB) DCA 802.11n Channel Width...................... 20 MHz DCA Minimum Energy Limit....................... -95 dBm Channel Energy Levels Minimum...................................... unknown Average...................................... unknown Maximum...................................... unknown Channel Dwell Times Minimum...................................... 0 days, 00 h 18 m 39 s Average...................................... 0 days, 00 h 18 m 39 s Maximum...................................... 0 days, 00 h 18 m 39 s 802.11a 5 GHz Auto-RF Channel List Allowed Channel List......................... 36,40,44,48,52,56,60,64,149,153,157,161 Unused Channel List.......................... 165 DCA Outdoor AP option.......................... Disabled
You can see interference, load, coverage, AP neighbor information from “show ap auto-rf 802.11a <ap-name> ” command. Here is an example for that.
(WLC1) >show ap summary Number of APs.................................... 1 Global AP User Name.............................. Not Configured Global AP Dot1x User Name........................ Not Configured AP Name Slots AP Model Ethernet MAC Location Port Country Priority ------------------ ----- -------------------- ----------------- ---------------- ---- ------- ------ LWAP-02 2 AIR-LAP1252AG-N-K9 54:75:d0:dd:a4:88 default location 1 AU 1 (WLC1) >show ap auto-rf 802.11a LWAP-02 Number Of Slots.................................. 2 AP Name.......................................... LWAP-02 MAC Address...................................... 54:75:d0:dd:a4:88 Slot ID........................................ 1 Radio Type..................................... RADIO_TYPE_80211a Sub-band Type.................................. All Noise Information Noise Profile................................ PASSED Channel 36................................... -100 dBm Channel 40................................... -100 dBm Channel 44................................... -100 dBm Channel 48................................... -100 dBm Channel 52................................... -100 dBm Channel 56................................... -100 dBm Channel 60................................... -100 dBm Channel 64................................... -100 dBm Channel 149.................................. -98 dBm Channel 153.................................. -85 dBm Channel 157.................................. -98 dBm Channel 161.................................. -98 dBm Channel 165.................................. -98 dBm Interference Information Interference Profile......................... PASSED Channel 36................................... -128 dBm @ 0 % busy Channel 40................................... -128 dBm @ 0 % busy Channel 44................................... -128 dBm @ 0 % busy Channel 48................................... -128 dBm @ 0 % busy Channel 52................................... -128 dBm @ 0 % busy Channel 56................................... -128 dBm @ 0 % busy Channel 60................................... -128 dBm @ 0 % busy Channel 64................................... -128 dBm @ 0 % busy Channel 149.................................. -128 dBm @ 0 % busy Channel 153.................................. -128 dBm @ 0 % busy Channel 157.................................. -128 dBm @ 0 % busy Channel 161.................................. -128 dBm @ 0 % busy Channel 165.................................. -128 dBm @ 0 % busy Rogue Histogram (20/40_ABOVE/40_BELOW) ............................................. Channel 36................................... 1/ 0/ 0 Channel 40................................... 0/ 0/ 0 Channel 44................................... 0/ 0/ 0 Channel 48................................... 0/ 0/ 0 Channel 52................................... 0/ 0/ 0 Channel 56................................... 0/ 0/ 0 Channel 60................................... 0/ 0/ 0 Channel 64................................... 0/ 0/ 0 Channel 149.................................. 0/ 0/ 0 Channel 153.................................. 0/ 0/ 0 Channel 157.................................. 0/ 0/ 0 Channel 161.................................. 0/ 0/ 0 Channel 165.................................. 0/ 0/ 0 Load Information Load Profile................................. PASSED Receive Utilization.......................... 0 % Transmit Utilization......................... 0 % Channel Utilization.......................... 0 % Attached Clients............................. 1 clients Coverage Information Coverage Profile............................. PASSED Failed Clients............................... 0 clients Client Signal Strengths RSSI -100 dbm................................ 0 clients RSSI -92 dbm................................ 0 clients RSSI -84 dbm................................ 0 clients RSSI -76 dbm................................ 0 clients RSSI -68 dbm................................ 0 clients RSSI -60 dbm................................ 0 clients RSSI -52 dbm................................ 1 clients Client Signal To Noise Ratios SNR 0 dB.................................. 0 clients SNR 5 dB.................................. 0 clients SNR 10 dB.................................. 0 clients SNR 15 dB.................................. 0 clients SNR 20 dB.................................. 0 clients SNR 25 dB.................................. 0 clients SNR 30 dB.................................. 0 clients SNR 35 dB.................................. 0 clients SNR 40 dB.................................. 0 clients SNR 45 dB.................................. 1 clients Nearby APs AP 64:a0:e7:af:47:40 slot 1.................. -29 dBm on 40 (10.10.112.10) Radar Information Channel Assignment Information Current Channel Average Energy............... unknown Previous Channel Average Energy.............. unknown Channel Change Count......................... 0 Last Channel Change Time..................... Sat Mar 16 05:47:15 2013 Recommended Best Channel..................... 161 RF Parameter Recommendations Power Level.................................. 1 RTS/CTS Threshold............................ 2347 Fragmentation Threshold...................... 2346 Antenna Pattern.............................. 0 Persistent Interference Devices Class Type Channel DC (%%) RSSI (dBm) Last Update Time ------------------------- ------- ------ ---------- ------------------------ All third party trademarks are the property of their respective owners.
General settings of RRM can be view/modify under “Wireless ->802.11b/g/n or 802.11a/n ->RRM -> General” section.
The profile threshold configurations determine the threshold that trigger SNMP trap alarms to WCS. You can change default settings (as shown in the above) to a value appropriate to your environment.
APs periodically go off channel to record RRM measurment. The off-channel scanning approximately takes 50ms and is transparent to any associated clients. Channel duration is the interval (60 to 3600s) that AP has to scan all the channels. On 2.4 GHz band in USA, default interval is 180s, which means AP go off channel in every ~16s (180/11 to scan 11 channels in 2.4GHz).
Neighbor packet frequency is how often APs exchange neighbor messages. Default is 60s. This also use to maintain neighbor list. If AP does not receive neighbor messages for an hour it will remove that neighbor form the list.
RRM use Cisco Neighbor Discovery Packet (NDP) to gather neighbor RF information. Normally these packets are not encrypted & starting from 7.0.116.0 code onwards you can encrypt these. There are two modes (Protected & Transparent) available & by default it is transparent (which is send them as it is). You can use following CLI command to verify this.
(WLC1) >show advanced 802.11a monitor Default 802.11a AP monitoring 802.11a Monitor Mode........................... enable 802.11a Monitor Mode for Mesh AP Backhaul...... disable 802.11a Monitor Channels....................... Country channels 802.11a RRM Neighbor Discover Type............. Transparent 802.11a AP Coverage Interval................... 180 seconds 802.11a AP Load Interval....................... 60 seconds 802.11a AP Noise Interval...................... 180 seconds 802.11a AP Signal Strength Interval............ 60 seconds
By using “config advanced 802.11a|802.11b monitor ndp-type protected” you can encrypt these packets.
config advanced 802.11a monitor ndp-type protected ! (WLC1) >show advanced 802.11a monitor Default 802.11a AP monitoring 802.11a Monitor Mode........................... enable 802.11a Monitor Mode for Mesh AP Backhaul...... disable 802.11a Monitor Channels....................... Country channels 802.11a RRM Neighbor Discover Type............. Protected 802.11a AP Coverage Interval................... 180 seconds 802.11a AP Load Interval....................... 60 seconds 802.11a AP Noise Interval...................... 180 seconds 802.11a AP Signal Strength Interval............ 60 seconds
Next post we will see DCA configuration settings.
Related Posts
1. RRM Basics
2. Configuring DCA
3. Configuring TPC
4. Configuring CHD
5. Configuring ClientLink
6.
7. Rogue Access Point Detection
