Now we have an overall idea about the control plane where the routing engine (RE) is and the forwarding plane where the packet forwarding engine (PFE) is, let’s have more information about the routing engine first.
The Routing Engine (RE) is based on X86 or PowerPC architecture. Depending on which Juniper device you are buying, it may come from one of the 2 named architectures. It is mainly called the brain of the device, and this term I have seen it in many documents written by Juniper. As being the brain of the device, that means it takes care of everything happening in the Juniper router.
Some of the functions that the Routing Engine has: maintain the Routing table, the bridging table and the primary forwarding table. I will explain them one by one:
- Routing table: it has the complete routing entries for all active and inactive routes in this table.
- Bridging table: it has the complete Layer 2 entries.
- Primary forwarding table: it copies the active route from the Routing Table and provide them to the Forwarding table in the routing engine which is also called the primary forwarding table.
In addition of those tasks, the routing engine has more tasks to do such as: controlling the interfaces, chassis, system management and access to the device. This means what? It means clearly that when we have access to the Juniper router via the CLI or via J-WEB (http or https) then this is controlled by the routing engine. This means that in case that our CLI crashes, we shouldn’t panic because the traffic will keep flowing via the Juniper router (in some other brands when you don’t have access to the CLI anymore then you should reboot the router because also the traffic will stop, which is not the case on Juniper fortunately 😊).
So, in summary, the routing engine is the brain of the device. It is a device by itself inside the Juniper router based on X86 or PowerPC architecture. It maintains the routing table, bridging table and primary forwarding table. It also has some other functions such as controlling the interfaces, chassis, system management and access to the device.
That’s all what I want you to know about the Routing engine in the Control Plane, let’s check now what is the function of the Packet Forwarding Engine in the Forwarding Plane.