SG uses the following on R3:
interface Virtual-Template13
ip address 167.1.135.3 255.255.255.0
!
interface Virtual-Template35
ip address 167.1.135.3 255.255.255.0
interface Serial1/0
no ip address
ip pim sparse-mode
encapsulation frame-relay
frame-relay interface-dlci 301 ppp Virtual-Template13
frame-relay interface-dlci 305 ppp Virtual-Template35
no frame-relay inverse-arp
question I have is, how does R3 know which DLCI to use to get to either R1 or R3?