multiple routing instance tables

[Amina]

I am new to Junos and trying to figure out how the router makes a decision which routing table to use in the case where multiple instances of routing tables are defined in addition to the master routing table.

Thanks..

[rickmur]

There are some default behaviors regarding multiple routing-tables.

By default:

• - all IPv4 unicast lookups are done using the inet.0 routing table. 
• - All IPv4 multicast lookups are done using inet.1
• - All BGP routes (so BGP routes with a next-hop in BGP) are looked up through inet.3
• - All IPv6 unicast lookups are done using inet6.0

And after all that default behavior you have the self-created routing tables using routing-instances. These are specific routing tables  that are only used for the interfaces belonging to the routing-instance.

Or you can steer traffic into the routing-instance using filter based forwarding (FBF).

Using rib-group functionality you can 'leake' route between routing tables.