This article describes the issue of DHCP combined with chassis cluster not being supported on J and SRX series devices in Junos releases below 12.1X46.
The DHCP server, client and relay functionality are supported on all SRX and J-series platforms and Firefly Perimeter. However a limitation is that the DHCP server, client and relay features are not supported in all Junos releases, if the device is participating in a chassis cluster.
Support for DHCP Relay in a chassis cluster has been introduced in Junos 12.1X46-D10 on all SRX platforms.
Support for DHCP Server and Client in a chassis cluster has been introduced in Junos 12.1X47-D10 on all SRX platforms and Firefly Perimeter.
For confirming if a feature is supported on your platform and software release refer to the Juniper Pathfinder Feature Explorer.
Note: It was already possible to configure DHCP in a cluster in earlier releases and it would work, however it was not officially supported and could in some cases lead to issues.