How to pass RIP routes between spokes (connected through a hub subif)

R3 (100.0.0.3) is the hub, R1 (100.0.0.1) & R2 (100.0.0.2) are the spokes.

The easy way

! R3
!---
interface Serial1/0.1 multipoint
 no ip split-horizon

The clever way

! R1
!---
router rip
 neighbor 100.0.0.2

! R2
!---
router rip
 neighbor 100.0.0.1

The ugly way

! R3
!---
interface Serial1/0.1 multipoint
 frame-relay interface-dlci 301 ppp Virtual-Template31
 frame-relay interface-dlci 302 ppp Virtual-Template32
!
interface Virtual-Template31
 ip address 100.0.0.3 255.255.255.0
!
interface Virtual-Template32
 ip address 100.0.0.3 255.255.255.0

! R1
!---
interface Serial1/0
 encapsulation frame-relay
 frame-relay interface-dlci 103 ppp Virtual-Template31
!
interface Virtual-Template31
 ip address 100.0.0.1 255.255.255.0

! R2
!---
interface Serial1/0
 encapsulation frame-relay
 frame-relay interface-dlci 203 ppp Virtual-Template32
!
interface Virtual-Template32
 ip address 100.0.0.2 255.255.255.0

Choose what ever suits your needs.