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- Are both incoming and outgoing calls affected?
- Is the internal telephony also affected?
- Are all destination numbers affected?
- What status does the used line in the line area of the STARFACE show?
- Does the error change after a restart of the affected line or the STARFACE?
- If the error changes after a restart of external components, such as NTBAs or routers?
- Only with ISDN maps: Does the error change after cross exchange of the used ports (Only with ISDN maps)?
- Has there been any changes to the existing network infrastructure (e.g., firewall rules or DHCP server)?
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