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360 Chapter 10: X.25/Frame Relay Topologies
point or leased lines. Subinterfaces are definitely recommended. The trade-off is that, because
with multipoint every router is on the same network, there are more routes in the routing table,
because each subinterface has its own network. But it also makes troubleshooting easier,
because split horizon issues are difficult to troubleshoot.
Figure 10-20
Frame Relay Subinterfaces
Design Options
This section discusses some design considerations to be used with Frame Relay. There are
several topology options, including NBMA full mesh, hierarchical full mesh, and star (hub-and-
spoke) networks. One of the major issues is, of course, split horizon and how the design
addresses that.
Router B
Cloud
Router C
Router A
192.168.2.0 Network
192.168.1.0 network
Interface serial 0.200
Interface serial 0.100
Subinterfaces create
separate networks
Router B
interface Serial0
no ip address
encapsulation frame-relay
no frame-relay inverse-arp
frame-relay lmi-type ansi
!
interface Serial0.100 point-to-point
ip address 192.168.1.1 255.255.255.252
no ip directed-broadcast
frame-relay interface-dici 100
!
interface Serial0.200 point-to-point
ip address 192.168.2.1 255.255.255.252
no ip directed-broadcast
frame-relay interface-dici 200
87200333.book Page 360 Wednesday, August 22, 2001 2:53 PM