Voice Over Wireless LAN (VoWLAN) Troubleshooting Checklist
Published: June 4, 2010
Revised: June 4, 2010
Voice Over Wireless LAN (VoWLAN) Troubleshooting Checklist
The following is a checklist that is recommended when troubleshooting a Voice Over Wireless LAN (VoWLAN). It also defines best practices and additional options that may need to be taken into consideration.
Table 1-1 VoWLAN checklist
Recommendation
Best Practice
May Consider
Done
Verify an AP can be seen from the phone at -67 dBm or better in all areas to be covered. You also need to verify that the AP sees the phone at -67 dBm or better in all areas as well.
X
Ensure that the SNR is always 25 dB or higher in all areas to provide coverage.
X
Verify that channel utilization is under 50%.
X
Configure voice WLAN to use the 802.11a band.
X
If using EAP authentication, ensure that fast roaming is supported such as CCKM.
X
WMM should be allowed or required for the voice WLAN.
X
Voice WLAN should be marked with Platinum QoS.
X
Platinum QoS profile should have the 802.1p bits set to 6.
X
Verify the switch ports used to connect to the controller are set to trust CoS and ports to APs and uplinks are set to trust DSCP.
X
Verify that Call Admission Control is enabled globally for the radios.
X
Verify that Load-based CAC is enabled under Call Admission Control.
X
Ensure that Load Based CAC (7920 AP CAC) under the WLAN is enabled for the voice WLAN if the network has a mix of 7920 and 792xG Series wireless IP phones.
X
Ensure that Client Based CAC (7920 Client CAC) under the WLAN is disabled for the voice WLAN.
X
Verify that the EDCA profile on the controller is set to Voice Optimized.
X
Verify that Low Latency MAC is disabled.
X
Verify that the 12 Mbps data rate is enabled (default PHY rate of the phone).
X
If using 802.11b/g disable the 1, 2, 5.5, 6, and 9 Mbps data rates if possible.
X
If using 802.11a disable the 6 and 9 Mbps data rates if possible.
X
Verify coverage is designed for 24 Mbps to maximize throughput. Optionally disable 36-54 Mbps.
X
Optionally disable 36-54Mbps
Verify that Aggressive Load Balancing is disabled.
X
Disabled ARP unicast if running a pre-4.2 image on the controller.
X
Verify that DTPC is enabled so that the client and AP match tx power levels.
X
Verify the Beacon interval is set to 100 ms.
X
A DTIM of 2 is recommended.
X
Ensure DHCP required is not enabled for the voice WLAN.
X
Ensure that Aironet IE is enabled for the voice WLAN.
X
Verify that Client MFP is set to Optional or Disabled.
X
Session timeout for the WLAN should not be too short (300 seconds or more).
X
Verify that peer-to-peer blocking is disabled.
X
If using TKIP encryption, disable the hold down timer on the voice WLAN to prevent MIC errors from disrupting voice.
X
Verify that the radio of the AP has multiple antennas and that diversity is enabled.
X
Ensure controllers are configured for Symmetric Mobility if phones will be roaming between controllers.
X
Validate the virtual interface address is the same across all controllers in the same mobility group.
X
Validate that the mobility status shows as UP between all controllers in the same mobility group.
X
Enable Traffic Stream Metrics collection on the controller.
X
DCA Channel Sensitivity set to High to reduce chance of channel changes during business hours.
X
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