Asterisk PJSIP: Provider Caller ID (Latest Versions)

Caller ID configuration is one of the most misunderstood parts of SIP provider integration in Asterisk.

Many deployments assume that setting a caller ID in the dialplan automatically guarantees it will appear on the customer’s phone. In reality, the final caller ID depends on:

• Asterisk dialplan configuration
• SIP headers sent to the provider
• Provider security and anti-spoofing policies
• National telecom regulations

Because of these multiple layers, caller ID problems are extremely common in real production environments.

How Caller ID Travels in an Outbound SIP Call

Understanding the complete signaling path is essential.

1. Dialplan sets CALLERID(num) and CALLERID(name)
2. Asterisk inserts values into SIP headers such as:
   • From
   • P-Asserted-Identity (PAI)
   • Remote-Party-ID (RPID)
3. SIP provider validates whether the caller ID is allowed
4. Provider either:
   • Passes caller ID to PSTN/mobile network
   • Replaces it with an approved DID
   • Rejects the call entirely

This explains why caller ID issues are often caused by provider policy, not Asterisk misconfiguration.

Basic Caller ID Configuration in Dialplan

[outbound]
exten => _X.,1,NoOp(Outbound call with caller ID)

 same => n,Set(CALLERID(name)=Support)
 same => n,Set(CALLERID(num)=1800123456)

 same => n,Dial(PJSIP/provider-endpoint/${EXTEN},60)
 same => n,Hangup()

This sets the caller ID inside Asterisk, but the provider may still override it.

Provider-Approved Caller ID Requirement

Modern SIP providers enforce strict anti-spoofing rules.

Typical restrictions:

• Only verified DID numbers can be used
• Random mobile numbers are rejected
• CLI must belong to the same account or trunk

If violated, providers usually respond with:

• 403 Forbidden
• 404 Not Found
• Silent caller ID replacement

Setting Caller ID at the PJSIP Endpoint Level

Some providers require caller ID to be defined in the endpoint rather than only in the dialplan.

[provider-endpoint]
type=endpoint
from_user=1800123456
from_domain=sip.provider.com
trust_id_outbound=yes
send_pai=yes
send_rpid=yes

Important options explained:

• from_user → primary CLI sent in SIP From header
• trust_id_outbound → allows dialplan caller ID to pass
• send_pai / send_rpid → enables identity headers required by providers

Real-World Caller ID Failure Scenarios

1. Call Rejected with 403 Forbidden

• Cause → CLI not approved by provider
• Fix → use verified DID or configure from_user

2. Call Connects but Wrong Caller ID Appears

• Cause → provider rewriting CLI
• Fix → request CLI mapping from provider

3. Anonymous or “Unknown” Caller ID

• Cause → missing PAI/RPID headers
• Fix → enable send_pai and send_rpid

Debugging Caller ID Problems Step-by-Step

1. Enable SIP Logging

pjsip set logger on

Check outbound INVITE headers:

• From
• P-Asserted-Identity
• Remote-Party-ID

2. Capture Packets with tcpdump

sudo tcpdump -i any -s 0 -w callerid.pcap udp port 5060

Open in Wireshark → verify actual SIP headers sent to provider.

3. Compare Provider Response

• If provider rewrites CLI → policy issue
• If provider rejects → permission issue

Caller ID Rules in Different Countries

Telecom regulations often restrict caller ID spoofing.

• India → strict CLI ownership enforcement
• Europe → STIR/SHAKEN-style verification expanding
• USA → strong anti-spoofing compliance requirements

Always design caller ID logic based on legal telecom compliance, not just technical capability.

Best Practices for Stable Caller ID Delivery

• Use provider-verified DID numbers only
• Configure caller ID at both dialplan and endpoint levels
• Enable PAI/RPID headers when required
• Document provider CLI policies clearly
• Verify using SIP logs and packet capture

Key Takeaway

Caller ID is not controlled by Asterisk alone. It is a cooperation between:

• Dialplan configuration
• PJSIP endpoint headers
• Provider authorization rules
• Telecom regulations

When these layers are aligned, outbound calls display the correct identity reliably. When they are not, failures are inevitable.