DHCP Option 150 vs Option 66: Key Differences and Best Practices
Selene Gong
DHCP Option 150 and Option 66 are DHCP options used to direct clients, particularly Cisco IP phones, to a TFTP server for configuration and firmware downloads. Although their goals overlap, they differ significantly in information delivery, configuration, and deployment scenarios.
Option 150: Provides the IP address of the TFTP server directly, with no DNS resolution needed.
Option 66: Provides the hostname or URL of the TFTP server, requiring DNS resolution before connecting.
2. Configuration Flexibility
Option 150:
Simple IP address input. Can specify multiple servers using hexadecimal concatenation. Configured with commands like option 150 ip on Cisco routers and some switches.
Option 66:
Uses ASCII strings for hostnames/URLs. Often combined with Option 160 to specify call control platforms during migrations (e.g., Webex Calling or Broadworks).
3. Deployment Scenarios
Option 150:
Standard method in local CUCM deployments. Used for routine firmware upgrades and zero-touch provisioning.
Option 66:
Used in migrations to MPP firmware. Ideal for cloud-based TFTP services with dynamic IPs.
Comparison Table
When to Use Each Option
Use Option 150 for local, static IP TFTP servers and standard deployments to minimize DNS dependency.
Use Option 66 for cloud-based or migration scenarios where the TFTP server IP may vary.
Can Both Options Be Used Simultaneously?
DHCP servers can provide both, but Cisco phones typically prefer Option 150 when available. It's best to choose one based on your deployment needs.
Will Option 66 Replace Option 150?
No. Both coexist serving different scenarios — Option 150 remains standard for local CUCM, Option 66 for cloud and migration cases.
FAQ
Q1.Can Option 150 and Option 66 be used together?
Yes, but Cisco phones usually prefer Option 150. Choose based on deployment requirements.
Q2.Which option is better for Cisco phones?
Depends on the environment: Option 150 for local CUCM; Option 66 for firmware migrations and cloud deployments.
