SIP error codes and troubleshooting

SIP 4xx — client errors

Code	Meaning	Fix
400	Bad request	Review SIP headers / SDP
401	Unauthorized	Check digest credentials
403	Forbidden	IP not whitelisted — check ACL
404	Not found	Verify phone number mapping
408	Request timeout	Check firewall / reachability
415	Unsupported media	Enable G.711; disable other codecs
480	Temporarily unavailable	Check PBX/SBC availability
484	Address incomplete	Use E.164 for numbers
486	Busy	Destination busy — normal
488	Not acceptable	SDP/codec mismatch — G.711

SIP 5xx — server errors

Code	Meaning	Fix
500	Server error	Retry
502	Bad gateway	Upstream routing — retry
503	Service unavailable	Check network / routing
504	Gateway timeout	Check firewall latency

Audio issues (no SIP error)

Symptom	Cause	Fix
No audio both ways	RTP blocked	Open UDP 10000–40000
One-way audio	NAT / firewall	Public IP in SDP; media allowlist
Audio drops mid-call	RTP idle timeout	Adjust firewall timeout

API error codes

Code	HTTP	Meaning	Fix
1000	404	Resource not found	Verify trunk SID / phone number ID
1001	400	Mandatory parameter missing	Check required fields
1002	400	Invalid parameter	Validate E.164, IP, JSON
1007	400	Malformed JSON	Fix JSON syntax
1008	409	Duplicate resource	Already configured — safe to ignore
1011	415	Wrong content type	Content-Type: application/json

Debug checklist

1. Confirm trunk status is active
2. Outbound: ACL or credentials match the egress IP / digest on your platform
3. Inbound: destination URI + Connect applet sip:<trunk_sid> + DID mapped to flow
4. Capture SIP traces (sngrep / Wireshark) and Call SIDs for support

Related

• Network & firewall
• Dynamic SIP Trunking API
• Docs portal: SIP Error Codes