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Go to the Options: Network tab on the Web Admin Panel. Alternatively, hook a keyboard and monitor to the PBX to set up the static IP and DNS (refer to the Installation guide for more information).
Make sure that the PBX is configured to use public DNS servers. If you need suggestions and you're in the U.S., 8.8.8.8 (Google DNS) and 4.2.2.2 (Level 3 Communications) are good primary and secondary choices. Or use those that your ISP supplies.
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For more information and workarounds, please refer to Setting the Boot Server (in IP Phones).
Reference / other info
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(In most cases with Windows Domain Controllers, we recommend using the directions above, under "Domain Controller Changes") However, if needed: Please read DNS Forwarder
Using a Local DNS Zone in your existing DNS Server
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