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300-365 · Question #39

After a wireless deployment, users report that wireless voice clients are experiencing an unacceptable amount of delay while roaming during a call on the Cisco Unified 7925 Series phones. The…

The correct answer is C. The access points for that floor are salt and peppered across multiple controllers and should be. Distributing APs from the same coverage area across multiple controllers forces voice clients to perform slower inter-controller roams, introducing latency that is unacceptable for active calls.

Wireless Troubleshooting and Optimization

Question

After a wireless deployment, users report that wireless voice clients are experiencing an unacceptable amount of delay while roaming during a call on the Cisco Unified 7925 Series phones. The customer environment consists of multiple controllers, all running 7.4.121.0 code, operating in a centralized deployment. What configuration issue is most likely contributing to the problem?

Options

  • AThe authentication should be set to WPA2-PSK to allow for 802.11n speeds for the Cisco Unified
  • BThe access points on that floor are all on one controller and should be load balanced evenly
  • CThe access points for that floor are salt and peppered across multiple controllers and should be
  • DThe wireless phones are operating in the 2 4 GHz band and should be configured for the 5 GHz

How the community answered

(23 responses)
  • A
    9% (2)
  • B
    17% (4)
  • C
    61% (14)
  • D
    13% (3)

Why each option

Distributing APs from the same coverage area across multiple controllers forces voice clients to perform slower inter-controller roams, introducing latency that is unacceptable for active calls.

AThe authentication should be set to WPA2-PSK to allow for 802.11n speeds for the Cisco Unified

Switching from WPA2-Enterprise to WPA2-PSK does not reduce roaming latency; mechanisms like 802.11r fast BSS transition or CCKM address roaming delay, not the authentication method itself.

BThe access points on that floor are all on one controller and should be load balanced evenly

Load balancing APs within a single controller improves capacity distribution but does not resolve inter-controller roaming latency, which is the root cause identified in the multi-controller environment.

CThe access points for that floor are salt and peppered across multiple controllers and should beCorrect

When APs covering the same floor are anchored to different WLCs, a roaming voice client must complete an inter-controller mobility handoff, which involves mobility tunnel negotiation and client state re-establishment between WLCs - this additional latency causes audible gaps and degraded voice quality. Consolidating floor APs onto a single WLC ensures intra-controller roaming, which completes far faster and maintains call continuity.

DThe wireless phones are operating in the 2 4 GHz band and should be configured for the 5 GHz

Moving clients to 5 GHz can improve throughput and reduce co-channel interference but does not address the inter-controller mobility handoff delay that is causing the voice roaming problem.

Concept tested: Inter-controller roaming latency impact on VoWLAN

Source: https://www.cisco.com/c/en/us/td/docs/wireless/controller/8-5/config-guide/b_cg85/roaming.html

Topics

#inter-controller roaming#voice roaming delay#centralized deployment#AP placement

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