Rib-groups simple example.

We created two routing instances: test1 and test2, each instances has one interface in it:
    test1 - vlan.641:     172.16.10.1/24
    test2 - vlan.642:       172.16.20.1/24

# show routing-instances
test1 {
    instance-type virtual-router;
    interface vlan.641;

}
test2 {
    instance-type virtual-router;
    interface vlan.642;
}

Routing table looks like this: