> ## Documentation Index > Fetch the complete documentation index at: https://plivo.com/docs/llms.txt > Use this file to discover all available pages before exploring further. # SIP Trunking (Zentrunk) > Zentrunk SIP trunking setup, configuration, and troubleshooting Frequently asked questions about Zentrunk, Plivo's cloud-based SIP trunking service. *** ## What is Zentrunk? Zentrunk is Plivo's cloud-based SIP trunking service that connects IP PBX systems to PSTN and mobile networks. *** ## What SIP methods does Zentrunk support? **Supported:** ACK, BYE, CANCEL, INVITE, OPTIONS, REFER, UPDATE **Not supported:** INFO, MESSAGE, PRACK, PUBLISH, REGISTER, SUBSCRIBE REFER is used for mid-call transfers. See [SIP REFER](/sip-trunking/concepts/sip-refer) for details. *** ## What codecs and encryption are supported? * **Codecs:** PCMA, PCMU * **Encryption:** TLS for signaling, SRTP for media * **DTMF:** RFC-2833 format *** ## Are call recording and T.38 fax supported? No. Call recording and T.38 fax are not supported features. *** ## Where are Zentrunk's data centers located? | Region | Location | | ------------- | -------------------------- | | North America | North California, Virginia | | Europe | Frankfurt | | South America | São Paulo | | Asia Pacific | Singapore, Sydney, Mumbai | *** ## What are the default CPS limits? | Level | Default | Description | | ------------- | ------------ | ---------------------------------------- | | Account-level | 2 CPS | Total calls per second across all trunks | | Trunk-level | Configurable | Allocated per trunk from account pool | *** ## Can CPS limits be increased? Yes. Contact [Plivo Sales](https://www.plivo.com/contact/sales/) to increase your CPS allocation. *** ## How does call queuing work with CPS? * Calls exceeding trunk CPS fail immediately * Calls exceeding account CPS queue for processing *** ## What IP addresses must be whitelisted? | Region | CIDR Blocks | | ---------------- | ----------------------------------------------------------- | | North California | `13.52.9.0/25`, `216.120.187.128/26` | | Virginia | `18.214.109.128/25`, `18.215.142.0/26`, `204.89.148.128/26` | | Frankfurt | `3.120.121.128/26` | | São Paulo | `18.228.70.64/26` | | Sydney | `13.238.202.192/26` | | Singapore/Mumbai | Check [Zentrunk documentation](/sip-trunking) | **Ports:** 5060 (UDP/TCP), 5061 (TLS) for signaling; 10000-30000 (UDP/TCP) for media *** ## What authentication methods are available? * IP Access Control Lists * Username/password credentials * Both combined *** ## What are the resource limits? | Resource | Limit | | ------------------- | --------------------------- | | Trunks per account | 100 (recommended) | | IP ACLs per account | Unlimited | | Concurrent calls | Unlimited (elastic scaling) | *** ## How do SIP OPTIONS pings work? * Send pings to the outbound trunk URI only * Maximum frequency: 1 ping per 10-15 seconds * Higher frequency may trigger blocking *** ## Why must I use Plivo numbers as caller ID? Plivo numbers are required as caller ID for all outbound calls. Using non-Plivo numbers results in an `unknown_caller_id` hangup. **Options:** * Rent numbers through the Plivo console * Port existing numbers to Plivo * Contact [Plivo Support](https://support.plivo.com) for special cases *** ## Which countries guarantee domestic caller ID? Plivo guarantees domestic CLI in: US, Canada, UK, Australia, Italy, Peru, and France (beta). *** ## Why are premium numbers blocked? Zentrunk blocks calls to premium-rate numbers to prevent toll fraud (IRSF - International Revenue Share Fraud). *** ## How can I call premium numbers? 1. Contact [Plivo Support](https://support.plivo.com) 2. Provide use case details 3. Wait for validation (48+ hours) If a number is incorrectly classified, support can review it. *** ## How does Zentrunk pricing work? Call rates vary by originating country, not just destination. For example, calls to Germany from Europe cost less than from outside Europe. Check [Zentrunk Pricing](https://www.plivo.com/pricing/zentrunk/) for current rates. *** ## What are abandoned and short duration call charges? When the percentage of abandoned or short-duration calls exceeds 20% of your monthly call volume, a per-call surcharge applies to the excess calls. | Type | Threshold | Surcharge | | --------------------------- | ------------- | ------------------------ | | Abandoned calls (0 seconds) | > 20% monthly | \$0.005 per excess call | | Short calls (≤6 seconds) | > 20% monthly | \$0.0025 per excess call | **Calls to India are excluded** from short-duration surcharges. The 20% threshold and surcharges apply only to calls to non-India destinations. *** ## How do I access call detail records? 1. Navigate to **Zentrunk > Logs** in the console 2. Filter CDRs as needed 3. Click **Export** to download *** ## What debug information is available? * Call details (basic info) * Call stats (origination, termination, trunk info) * SIP logs (PCAP, last response, codec) No charge for debug logs. *** ## What does `unknown_caller_id` hangup mean? A non-Plivo number was used as caller ID. Use a Plivo number or port your number. *** ## What does `destination_country_barred` mean? Geo permissions are not enabled for that country. Enable the destination country in your console. *** ## What CLI prefixes are blocked in Australia? Per ACMA regulations: `+6113`, `+611300`, `+611800`, `+611900` *** ## What traffic is prohibited in China? * Gambling, financial services, cryptocurrency * Marketing/spam calls * Fraudulent calls * Politically sensitive content *** ## What are China's outbound calling requirements? * Cannot use Chinese caller IDs * Maintain average call duration over 3 minutes * Avoid high unanswered rates * Don't use toll-free numbers *** ## What are China's inbound calling requirements? Chinese numbers can only receive calls from within China. *** ## What systems work with Zentrunk? * **IP PBX:** FreeSWITCH, Asterisk, FreePBX, 3CX, FusionPBX * **Session Border Controllers** * **Softphones:** Zoiper, X-Lite/Bria *** ## How do I set up a softphone with Zentrunk? 1. Create an account in your softphone 2. Uncheck "register with domain and receive calls" 3. Configure with your Zentrunk SIP URI *** ## How do I map numbers to inbound trunks via API? Use the [Account Phone Number API](/numbers/api/account-phone-number) with the `inbound trunk_id` parameter. *** ## Related Resources * [Voice API Overview](/docs/voice/voice-api) * [Voice Features](/docs/voice/voice-features) * [Zentrunk Quickstart](/sip-trunking/getting-started) * [Zentrunk API Reference](/sip-trunking/api/overview) * [PBX Integration Guides](/sip-trunking/interconnection-guides/overview) * [SIP REFER — Call Transfer](/sip-trunking/concepts/sip-refer)