# What is the fallback phone number in sipgate trunking? If you configure a caller ID number in your phone system, it is automatically transmitted to the called party. If this is not the case, or if the caller ID number cannot be transmitted in the format we require, sipgate sets a so-called fallback number. This can be set on the website in the **Trunk settings** set. ![Fallback number dialog](/files/ad35117651d3ec7978ab8a0007af8e256da01d5d) For outgoing calls, please set the desired caller ID number in the **E164**-**format** (i.e. international, without leading zeros or **"+" sign**) as a new header: ``` P-Preferred-Identity: ``` If you want to **suppress your number** customize the header as desired: ``` P-Preferred-Identity: Privacy: id ``` --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://help.sipgate.de/trunking/en/was-ist-die-fallback-rufnummer-bei-sipgate-trunking.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.