This and the next section (Filter-Based Forwarding) will move beyond the more customary IP routing topics to some of what makes IP routing in the Junos operating system so unique.
The Junos control plane is far more versatile than that of a typical IP router. Junos is not limited to one monolithic routing table, but rather can support hundreds and even thousands of distinct routing tables on the highest-end platforms.
Likewise, the Junos data plane is not restricted by traditional destination-based routing when making forwarding decisions (as you’ll explore in both this and the next section). It can make forwarding decisions based on nearly any relevant fields in the Layer 3 and Layer 4 headers.
The power and flexibility that is put in your hands by this combination of highly unique control plane and equally unique data plane is extraordinary. In an age when virtualization has become a buzzword, IP routing in Junos is the real deal. You will scratch the surface of Junos’s power in the following sections.
routing-instance is the basic building block for
constructing the multiplicity of custom routing tables, forwarding
entries, and routing protocol instantiations that are possible with the
Junos operating system.
In the Junos CLI configuration that follows, you will create a
routing-instance with its own
routing table, interface, and OSPF, as depicted in Figure 11-11.
Figure 11-11. Routing instances
Here you enter configuration mode ...