ACA Troubleshooting & Diagnostics 1 — Questions and Answers
Question 1: When an AudioCodes Mediant gateway returns SIP response '503 Service Unavailable' to outbound calls, the most likely cause is:
- The configured SIP proxy is unreachable or all proxy servers in the proxy set are down (Correct answer)
- An incorrect codec configuration
- A DTMF relay mismatch
- An expired TLS certificate on the local device
Correct answer: The configured SIP proxy is unreachable or all proxy servers in the proxy set are down
A 503 response typically indicates the gateway cannot reach any of the configured SIP proxies, either because they are down or because network connectivity to them is lost.
Question 2: Which AudioCodes tool provides real-time SIP message tracing directly from the web GUI without needing an external packet capture?
- SIP Ladder Diagram (Message Log / Syslog viewer) (Correct answer)
- Wireshark plugin
- SNMP MIB browser
- CDR report generator
Correct answer: SIP Ladder Diagram (Message Log / Syslog viewer)
The AudioCodes web GUI's Message Log displays a real-time SIP ladder diagram showing INVITE, 100 Trying, 180 Ringing, and other messages with timestamps for quick troubleshooting.
Question 3: A one-way audio issue on calls through an AudioCodes gateway is most commonly caused by:
- NAT traversal problems preventing RTP from reaching one endpoint (Correct answer)
- A SIP 488 codec mismatch
- An incorrect DTMF mode
- A TLS handshake failure
Correct answer: NAT traversal problems preventing RTP from reaching one endpoint
One-way audio typically occurs when RTP can flow in one direction but NAT or firewall blocks prevent the return path, causing only one side to hear audio.
Question 4: Which AudioCodes CLI command shows active calls and their current state in real time?
- show voip calls active (Correct answer)
- debug sip call
- list sessions current
- show rtp streams
Correct answer: show voip calls active
The 'show voip calls active' command displays all currently active call legs with their SIP state, codec, and media information on AudioCodes Mediant devices.
Question 5: When troubleshooting AudioCodes OVOC connectivity to a managed device, which port must be open from the device to the OVOC server?
- UDP 161 (SNMP) and TCP 443 (HTTPS) (Correct answer)
- TCP 5060 (SIP) only
- UDP 5004 (RTP) only
- TCP 8080 (HTTP proxy)
Correct answer: UDP 161 (SNMP) and TCP 443 (HTTPS)
OVOC uses SNMP (UDP 161) for monitoring/traps and HTTPS (TCP 443) for configuration push and device communication, so both ports must be allowed through firewalls.
Question 6: What does a SIP '488 Not Acceptable Here' response indicate during call troubleshooting?
- The called party does not support any of the codecs offered in the SDP (Correct answer)
- The SIP proxy requires authentication
- The destination is busy
- The SIP URI was not found in the dial plan
Correct answer: The called party does not support any of the codecs offered in the SDP
A 488 response means the remote end rejected the SDP offer because none of the proposed codecs, media types, or parameters are acceptable, indicating a codec mismatch.
ACA Troubleshooting & Diagnostics 1
When an AudioCodes Mediant gateway returns SIP response '503 Service Unavailable' to outbound calls, the most likely cause is: