This article addresses the question of whether a GRE tunnel can be configured using a reth (redundant Ethernet) interface as the source on a Juniper SRX device running in chassis cluster mode. It also explains how to interpret the GRE interface name (gr-fpc/pic/port) when configuring tunnels in such a setup.

Yes, it is fully supported to configure a GRE tunnel using a reth interface as the source in a Juniper SRX cluster. This is the correct method when you want the GRE tunnel to remain active even after a failover between cluster nodes.

• The GRE interface name format (gr-0/0/0, gr-0/0/1, etc.) is purely logical and does not refer to a physical FPC, PIC, or port. You can use any available number; it is not tied to actual hardware.
• GRE is a software-based feature on SRX devices. It does not require a tunnel services PIC or any special hardware to function.