DHCP Option 156 Configuration: Setting Up Shoretel IP Phones

Adding DHCP Option 156 for a ShoreTel IP Phone System

ShoreTel (Mitel) IP phones use DHCP Option 156 to automatically discover key configuration details — like the FTP server they should pull their configuration and firmware from — when they first boot on your network. Option 156 isn’t one of the standard options available by default in the Windows DHCP console, so you need to define it manually before phones can use it. On your DHCP server:

• Open the DHCP console and right-click your server (or the specific scope), then choose Set Predefined Options.
• Click Add to create a new option: set the name (e.g. “ShoreTel Option 156”), data type to String, and code to 156.
• Once defined, go into Scope Options for the relevant scope (or configure it at the server level for all scopes), enable option 156, and enter the ShoreTel-specific configuration string — this typically includes your FTP server address and other ShoreTel deployment parameters, formatted exactly as specified in ShoreTel’s own deployment documentation for your platform version.

Since the exact string format varies between ShoreTel platform versions, always confirm the precise syntax against the ShoreTel/Mitel deployment guide for your specific system version rather than reusing an example from a different deployment, as a malformed option 156 string will simply be ignored by the phones rather than throwing an obvious error.

Worth Knowing Before You Deploy This Today (Updated for 2026)

ShoreTel is now Mitel MiVoice Connect, and the platform is in active end-of-life wind-down: add-on and security-patch sales stopped at the end of 2024, extended licence/design support ended at the end of 2025, and full support is scheduled to run through 2029. The DHCP Option 156 mechanism itself is a phone-side boot behaviour and is unaffected by that timeline, but it’s worth factoring the platform’s support status into any new deployment or expansion of a ShoreTel/MiVoice Connect phone estate today.

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