Starting beginning of this book, I have explained briefly about the difference between the routing table and the forwarding table on Juniper. In this lesson, I am going to go a bit deeper with the explanation.

Let’s start with the routing table: It contains all the routing information learned by all routing protocols. This can be active and inactive routes, all of them are contained in the routing table. The routing table is situated in the control plane at the routing engine as you may already know.

The routing table will take all active routes and send them to the master forwarding table that is situated also in the control plane at the routing engine.

Let’s dig even more about the routing table.

Routing Table

• Contains all the routing information learn by all routing protocols
• Stores static routes, directly connected interface routes and routing information learned by all routing protocols
• It checks and selects the active routes to each destination

Junos maintains 3 routing tables:

• Unicast: stores routing information about all unicast routing protocols such as: BGP, RIP, OSPF, IS-IS
• Multicast: stores routing information about all multicast routing protocols such as: DVMRP, PIM
• MPLS: stores MPLS path and labeling

The following are the default routing tables in Juniper devices:

• 0 – default IPv4 unicast routing table
• 1 – IPv4 multicast forwarding cache
• 2 – unicast routes for multicast reverse path forwarding (RPF) lookup
• 3 – default IPv4 MPLS routing table
• 0 – default IPv6 unicast routing table
• 1 – IPv6 multicast forwarding cache
• 0 – for MPLS label switching operations
• 0 – for IS-IS routing

We can see that on the Juniper router using the following command:

As I am using only unicast on my router, then it shows the routing table inet.0

Let’s move to the forwarding table. The master forwarding table on the control plan will sent a copy to the forwarding table on the data plane via the internal link, and that table will be responsible to route the traffic coming to the Juniper router as all traffic will be coming and going from the data plane.

This is all what I wanted to show you in this lesson about the difference between the Routing table and the Forwarding table, hope you enjoyed it and see you in the upcoming lesson.