For example, to fully mesh a network of 10 nodes, 45 links are required??”10
(10 ??“ 1) / 2.
?– Star topology: Remote sites are connected to a central site that generally provides a
service or an application. The star topology, also known as a hub-and-spoke
con?¬?guration, is the most popular Frame Relay network topology. This is the least
expensive topology because it requires the least number of PVCs. In the ?¬?gure, the
central router provides a multipoint connection because it typically uses a single
interface to interconnect multiple PVCs.
By default, a Frame Relay network provides nonbroadcast multiaccess (NBMA)
connectivity between remote sites. An NBMA environment is treated like other broadcast
media environments, such as Ethernet, where all the routers are on the same subnet.
However, to reduce cost, NBMA clouds are usually built in a hub-and-spoke topology. With
a hub-and-spoke topology, the physical topology does not provide the multiaccess
capabilities that Ethernet does, so each router might not have separate PVCs to reach the
other remote routers on the same subnet. Split horizon is one of the main issues you
encounter when Frame Relay is running multiple PVCs over a single interface.
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