Why CLI format matters
On a CLI route the caller ID you send is the number the person sees. If it is malformed, the terminating network either replaces it, shows it as unknown, or rejects the call. Each of these lowers your answer rate, and on some destinations repeated bad CLIs get the traffic flagged as spoofed. What is a CLI route explains how caller ID travels end to end.
What the checker looks at
- Presence. Withheld values such as
anonymousorrestrictedfail. CLI routes need a real number. - Validity. The number must match a range and length in its national numbering plan.
- Trunk format. We expect country code plus number with no
+or00. The checker shows the corrected value. - Number type. Premium-rate numbers fail. Toll-free numbers warn, because many networks reject them as CLI and they often cannot be called back from abroad.
- Placeholder patterns. Long runs of the same digit, sequences such as 1234567, and ranges reserved for TV and film are rejected as obviously fake.
- Destination rules. Domestic and international CLI are treated differently, and some countries have specific rules.
Reading SIP headers
Caller ID can appear in the From header, in P-Asserted-Identity (PAI), or both. Many carriers, including us, use PAI when it is present and fall back to From. Paste either header and the checker takes the user part of the URI.
From: "Sales" <sip:[email protected]>;tag=8f2a
P-Asserted-Identity: <sip:[email protected]>
P-Asserted-Identity: <tel:+4930901820>If From and PAI carry different numbers, the call can be shown differently on different networks. Set both to the same value unless your carrier asks for something else.
Country rules that catch people out
Some countries block calls from abroad that present a domestic number, because that is what spoofed scam calls look like. The UK and Germany both do this. A CLI route avoids the problem by handing the call over inside the country, so it arrives as a domestic call. Brazil requires a 0303 number for telemarketing. In the US and Canada, STIR/SHAKEN attestation affects how the call is labelled. CLI rules by country has the full table.
Before a campaign
Check every caller ID in your dialer campaign settings, not just one. Confirm the dialer sends the value the checker suggests: place a test call and read the From and PAI headers in a SIP trace. Then follow the route acceptance test plan to confirm the number reaches the handset unchanged.
Last reviewed by the CLIRoutes routing team. Spotted a numbering change? Tell us.