Business Phone Systems Troubleshooting & Maintenance 1 — Questions and Answers
Question 1: What is the first step when diagnosing poor VoIP call quality on a business phone system?
- Run a network test to check latency, jitter, and packet loss between the phone and the SIP server (Correct answer)
- Replace the IP phone hardware immediately
- Contact the internet service provider to upgrade bandwidth
- Restart the entire PBX system
Correct answer: Run a network test to check latency, jitter, and packet loss between the phone and the SIP server
Network performance testing identifies whether call quality issues stem from the LAN, WAN, or ISP rather than the phone hardware or PBX.
Question 2: What causes one-way audio in a VoIP call?
- A NAT or firewall issue blocking RTP media from flowing in one direction (Correct answer)
- A faulty microphone on one of the phones
- Insufficient bandwidth for the selected codec
- An incorrectly configured voicemail greeting
Correct answer: A NAT or firewall issue blocking RTP media from flowing in one direction
One-way audio usually occurs when a NAT or firewall blocks RTP packets traveling in one direction while allowing the other.
Question 3: What does it mean when a SIP phone shows 'Registration Failed'?
- The phone cannot authenticate with the SIP registrar, usually due to wrong credentials, server address, or network issue (Correct answer)
- The phone's hardware warranty has expired
- The phone number has been disconnected by the carrier
- The phone's SIP license has not been activated
Correct answer: The phone cannot authenticate with the SIP registrar, usually due to wrong credentials, server address, or network issue
Registration failure means the SIP REGISTER request was rejected, typically because of incorrect username, password, SIP server address, or a network block.
Question 4: What tool can be used to capture and analyze SIP and RTP packets to diagnose VoIP issues?
- Wireshark (Correct answer)
- Ping
- Traceroute
- Nmap
Correct answer: Wireshark
Wireshark captures network packets and has built-in VoIP analysis tools that can decode SIP signaling and reconstruct RTP audio streams.
Question 5: What does 'echo' in a VoIP call typically indicate?
- Acoustic echo from a speakerphone or sidetone misconfiguration in the phone hardware (Correct answer)
- A duplex mismatch on the network switch
- Corrupted codec negotiation between the two endpoints
- A DNS resolution failure at call setup
Correct answer: Acoustic echo from a speakerphone or sidetone misconfiguration in the phone hardware
Echo is typically caused by acoustic feedback from speakers near microphones or by improper echo cancellation settings in the phone or gateway.
Question 6: What is the purpose of a ping test when troubleshooting VoIP connectivity?
- Measures round-trip latency and packet loss between a phone or PC and the SIP server (Correct answer)
- Tests audio quality between two IP phones
- Verifies that the correct codec is being used
- Checks if the SIP registrar is accepting new registrations
Correct answer: Measures round-trip latency and packet loss between a phone or PC and the SIP server
Ping sends ICMP echo requests to measure network round-trip time and identify packet loss, helping isolate network-layer VoIP problems.
Business Phone Systems Troubleshooting & Maintenance 1
What is the first step when diagnosing poor VoIP call quality on a business phone system?