---
title: SIP Error Codes & Troubleshooting Guide
slug: dynamic-sip-trunking/sip-error-codes-and-troubleshooting-guide
docTags: 
createdAt: 2026-01-24T09:04:48.536Z
---

 This table lists **SIP response codes you may encounter**, what they usually mean in real deployments, **where the issue most likely lies**, and **what to check next**.

## 1) Provisional Responses (1xx – Informational)

| **SIP Code** | **Meaning**      | **What It Means**                        | **What to Check**            |
| ------------ | ---------------- | ---------------------------------------- | ---------------------------- |
| 100          | Trying           | SIP request received and being processed | Normal behavior              |
| 180          | Ringing          | Destination endpoint is ringing          | Normal behavior              |
| 183          | Session Progress | Early media (IVR / announcements)        | If audio missing → RTP ports |

## 2) Successful Responses (2xx)

| **SIP Code** | **Meaning** | **What It Means**           | **What to Check**       |
| ------------ | ----------- | --------------------------- | ----------------------- |
| 200          | OK          | Call successfully connected | If no audio → RTP / NAT |

## 3) Client Errors (4xx – Most Common)

| **SIP Code** | **Meaning**             | **Likely Root Cause**        | **What to Check**              |
| ------------ | ----------------------- | ---------------------------- | ------------------------------ |
| 400          | Bad Request             | Malformed SIP headers or SDP | SIP logs for invalid headers   |
| 401          | Unauthorized            | Authentication required      | Credentials (if applicable)    |
| 403          | Forbidden               | IP not allowed               | ACL / whitelisted IP           |
| 404          | Not Found               | Invalid DID or routing       | Phone number mapping           |
| 408          | Request Timeout         | No SIP response              | Firewall / reachability        |
| 410          | Gone                    | Number inactive or removed   | DID status                     |
| 415          | Unsupported Media       | Codec not supported          | Ensure **G.711 A-law** enabled |
| 480          | Temporarily Unavailable | Endpoint unreachable         | PBX availability               |
| 484          | Address Incomplete      | Invalid number format        | E.164 format                   |
| 486          | Busy Here               | Destination busy             | Normal behavior                |
| 488          | Not Acceptable Here     | SDP / codec mismatch         | G.711 A-law only               |

## 4) Server Errors (5xx)

| **SIP Code** | **Meaning**          | **Likely Root Cause**       | **What to Check**  |
| ------------ | -------------------- | --------------------------- | ------------------ |
| 500          | Server Error         | Internal processing failure | Retry call         |
| 502          | Bad Gateway          | Upstream routing issue      | Retry              |
| 503          | Service Unavailable  | Destination unreachable     | Network / routing  |
| 504          | Gateway Timeout      | No upstream response        | Firewall / latency |
| 580          | Precondition Failure | Media negotiation failed    | RTP / NAT          |

## 5) Global Failures (6xx)

| **SIP Code** | **Meaning**             | **Likely Root Cause**     | **What to Check** |
| ------------ | ----------------------- | ------------------------- | ----------------- |
| 600          | Busy Everywhere         | All endpoints busy        | Retry             |
| 603          | Decline                 | Call rejected by endpoint | PBX dialplan      |
| 604          | Does Not Exist Anywhere | Invalid number            | DID correctness   |
| 606          | Not Acceptable          | Media policy failure      | Codec / SDP       |

## 6) Media (Audio) Issues – No SIP Error Shown

These are **the most common issues** and do **not always show SIP error codes**.

| **Symptom**                  | **Likely Cause** | **What to Check**     |
| ---------------------------- | ---------------- | --------------------- |
| No audio both ways           | RTP blocked      | UDP 10000–40000 open  |
| One-way audio                | NAT / firewall   | Public IP in SDP      |
| Audio drops after answer     | RTP timeout      | Firewall idle timeout |
| IVR audio but no agent audio | Asymmetric RTP   | Symmetric RTP enabled |

## 7) Codec Requirements (India)

| **Item**        | **Requirement**  |
| --------------- | ---------------- |
| Supported codec | **G.711 A-law**  |
| Other codecs    | Not supported    |
| Common failure  | 415 / 488 errors |

Ensure:

- G.711 A-law is enabled
- No other codec is forced ahead of it
- Transcoding is disabled (recommended)

## 8) API-Level Errors (Exotel)



| **API Error Code** | **HTTP Status** | **Meaning** | **What It Indicates** | **Common Endpoints** | **What the Customer Should Do** |
| ------------------ | --------------- | ----------- | --------------------- | -------------------- | ------------------------------- |

| **1000** | 404 | Not Found | Resource does not exist | POST /trunks/\{trunk\_sid}/phone-numbers<br />POST /trunks/\{trunk\_sid}/whitelisted-ips<br />POST /trunks/\{trunk\_sid}/destination-uris<br />PUT /trunks/\{trunk\_sid}/phone-numbers/\{id} | Verify trunk\_sid, phone number ID, or API path |
| -------- | --- | --------- | ----------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ----------------------------------------------- |

| **1001** | 400 | Mandatory parameter missing | Required field not sent in request | POST /trunks<br />POST /phone-numbers<br />PUT /phone-numbers/\{id} | Ensure all mandatory fields are present |
| -------- | --- | --------------------------- | ---------------------------------- | ------------------------------------------------------------------- | --------------------------------------- |

| **1002** | 400 | Invalid parameter | Field value is invalid or not allowed | POST /trunks<br />POST /destination-uris<br />POST /whitelisted-ips | Validate parameter format (IP, FQDN, E.164 number) |
| -------- | --- | ----------------- | ------------------------------------- | ------------------------------------------------------------------- | -------------------------------------------------- |

| **1007** | 400 | Invalid request body | JSON is malformed or not parsable | All POST / PUT APIs | Fix JSON syntax, remove trailing commas, ensure valid JSON |
| -------- | --- | -------------------- | --------------------------------- | ------------------- | ---------------------------------------------------------- |

| **1008** | 409 | Duplicate resource | Resource already exists | POST /trunks<br />POST /phone-numbers<br />POST /whitelisted-ips | Safe to ignore if config already exists |
| -------- | --- | ------------------ | ----------------------- | ---------------------------------------------------------------- | --------------------------------------- |

| **1011** | 415 | Unsupported content type | Incorrect Content-Type header | All POST / PUT APIs | Use Content-Type: application/json |
| -------- | --- | ------------------------ | ----------------------------- | ------------------- | ---------------------------------- |

## 9) Before Contacting Exotel Support

Please verify:

- SIP signaling port (443 / 5070) reachable
- UDP 10000–40000 open
- Correct Exotel IPs allowed
- Correct trunk domain used
- Correct mode (pstn or flow)
- Correct destination URI configured
- G.711 A-law enabled

## 10) When to Contact Exotel Support

Raise a ticket at **support.exotel.com(hello\@exotel.com)** only after verification.

Please share:

- Trunk SID
- CallSID
- Call direction (Inbound / Outbound)
- SIP response code (if any)
- Timestamp (with timezone)
- PBX SIP logs or PCAP (if available)