SonicOS/X 7 High Availability
Stateful Synchronization with DHCP
DHCP can be enabled on interfaces in both Active/Standby (non-stateful) and Stateful Synchronization modes.
Only the Active Security Appliance can get a DHCP lease. The Active Security Appliance synchronizes the DHCP IP address along with the DNS and gateway addresses to the Secondary Security Appliance. The DHCP client ID is also synchronized, allowing this feature to work even without enabling Virtual MAC.
During a failover, the Active Security Appliance releases the DHCP lease and, as it becomes the Active unit, the Secondary Security Appliance renews the DHCP lease using the existing DHCP IP address and client ID. The IP address does not change, and network traffic, including VPN tunnel traffic, continues to pass.
If the Active Security Appliance does not have an IP address when failover occurs, the Secondary Security Appliance starts a new DHCP discovery.
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