03: Routing Instances

Unique collection of routing tables, interfaces and routing protocol parameters.

A single device can imitate multiple devices.

The default routing instance is called master. The master routing instance includes routing tables inet.0, inet6.0. It might also contain other, private tables used by Junos; these can be ignored.

Configuring Routing Instances

edit routing-instances

Typical uses for user defined routing instances include filter-based forwarding, VPNs and system virtualisation.

Interfaces are assigned to routing instances in the routing-instances (instance name) hierarchy.

The command show interfaces terse routing-instance all will list interfaces, including the routing instance they are in.

A routing instance can contain its own tables, such as inet.0, just like the master routing instance.

A routing instance configuration can contain the usual routing configuration;

routing-instances {
    new-instance {
        instance-type virtual-router;
        interface ...;
        routing-options {
            static {
                route ...
            }
        }
        protocols {
            ospf {
                ...
            }
        }
    }
}

To test connectivity in the new instance;

ping ... routing-instance new-instance

To show a routing table;

show route table new-instance.inet.0

To show all routing instance;

show route instance

RIB Groups

Share routes between routing instances.

FBF: filter based forwarding - forward based on characteristics other then the destination IP address.

The following configuration options are used to share routes between multiple routing instances.

instance-import
instance-export
auto-export

Under edit routing-options, import-rib is the list of tables the routes are shared into and can include multiple tables. export-rib is the table the routes are taken from;

routing-options {
    rib-groups {
        (rib group name) {
            export-rib (routing table name);
            import-rib (routing table name);
            import-policy (policy-name);
        }
    }
}

In import-rib, the primary table (where the routes are taken from) must be listed first. If export-rib is present, it must be the primary table; hence export-rib is often omitted.

RIB Group Application

RIB groups are applied to routing instances, interfaces, or both.

OSPF routes should be shared from inet.0 to test.inet.0;

routing-options {
    rib-groups {
        test {
            import-rib [ inet.0 test.inet.0 ];
        }
    }
}

protocols {
    ospf {
        rib-group test;
        area 0.0.0.0 {
            ...
        }
    }
}

Routing Between Instances

A logical tunnel interface can be created to route between instances. A peer relationship is created over the logical interface. Logical tunnels are not supported on all Junos devices.

interfaces {
    lt-0/0/0 {
        unit 0 {
            encapsulation ethernet;
            peer-unit 1;
            family inet;
        }
        unit 1 {
            encapsulation ethernet;
            peer-unit 0;
            family inet;
        }
    }
}