Graceful Routing Engine Switchover
The extended DHCP local server and the DHCP relay agent applications both maintain the state of active DHCP client leases in the session database. The extended DHCP application can recover this state if the DHCP process fails or is manually restarted, thus preventing the loss of active DHCP clients in either of these circumstances. However, the state of active DHCP client leases is lost if a power failure occurs or if the kernel stops operating (for example, when the router is reloaded) on a single Routing Engine.
The extended DHCP local server and the DHCP relay agent support graceful Routing Engine switchover on all routing platforms that contain dual Routing Engines. To support graceful Routing Engine switchover, the extended DHCP application automatically mirrors (replicates) information about the state of bound DHCP clients from the master Routing Engine to the backup Routing Engine.
To enable graceful Routing Engine switchover support for the extended DHCP local server or DHCP relay agent, include the graceful-switchover statement at the [edit chassis redundancy] hierarchy level. You cannot disable graceful Routing Engine switchover support for the extended DHCP application when the router is configured to support graceful Routing Engine switchover.
For more information about using graceful Routing Engine switchover, see the Junos High Availability Configuration Guide.
